University of California • Berkeley Digitized by the Internet Archive in 2007 with funding from IVIicrosoft Corporation http://www.archive.org/details/coloradoferberitOOhessrich DEPARTMENT OP THE INTERIOR NITED STATES aEOLO( Bulletin 583 COLORADO FERBERITE AND THE WOLFRAMITE SERIES BY FRANK L. HESS AND WALDEMAR T, SCHALLER ^-:'v^-"">:-^ :"\ WASHINGTON UOY^RNMENT PRINTING OFFIC J 1911 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director Buiii.ETiN' 683 COLORADO FERBERITE AND THE WOLFRAMITE SERIES BY FRANK L. HESS AND WALDEMAR T. SCHALLER WASHINGTON GOVERNMENT PRINTING OFFICE 1914 F'^VV CONTENTS. Pagb. The MINERAL RELATIONS OP FERBERiTB, by Fraiik L. Hess 7 Geography and production 7 Characteristics of the ferberite 8 Geography and geology of the Boulder district 8 Occurrence, vein systems, and relations 9 Characteristics of the ore 10 Minerals associated with the ferberite 12 Adularia 12 Calcite 12 Chalcedony , 12 Chalcopyrite 12 Galena 12 Gold and silver 12 Hamlinite (?) 14 Hematite (specular) 15 Limonite 16 Magnetite 17 Molybdenite 17 Opal 17 Pyrite 17 Quartz 17 Scheelite 17 Sphalerite 17 Sylvanite 17 Spectroscopic examination 18 Crystallized ferberite 19 Composition of ferberite and other members of the wolframite series 19 Definition of ferberite and other members of the wolframite series 37 The excessof ferrous oxide and manganous oxide 38 Crystallography of ferberite from Bouldei^ County, Colo., by Walde- mar T. Schaller 40 Previous publications 40 General characters of the crystals 40 Mode of occurrence 40 Size 41 Color and cleavage 42 The measured crystals by localities 42 Axial elements 43 Calculation of values 43 Comparison of values 45 Forms and angles ^ New forms - ^"^ Forms previously described 52 Common forms ^ Bare forms ^ • VMAJUM ' 4 CONTENTS. Page. Crystallography op perberite from Boulder County, Colo.— Continued. Discussion of the prism zone 55 Habit 56 Combinations 60 Twinning 62 Description of measured crystals 65 Form system of the wolframite group 69 Critical study of forms 69 Forms and coordinate angles 71 Combinations observed on the wolframite group 73 Bibliography 74 ILLUSTRATIONS. Page. Plate I. Ay Ferberite inclosing finely brecciated granite, from Rogers tract, Nederland, Colo.; B, ''Peanut ore," ferberite inclosing finely brecciated pegmatite, from the Conger mine, Nederland, Colo. ... 10 II. Brecciated granite and pegmatite cemented by ferberite, from Town Lot mine, Nederland, Colo 11 III. Brecciated ferberite vein, showing crystals formed since brecciation, from Conger mine, Nederland, Colo 12 IV. A, Cut and polished crystal of brown ferberite from Winnebago claim, near RoUinsville, Colo.; B, Brecciated ferberite vein from the Conger mine, Nederland, Colo 13 V. Vug in a ferberite vein nearly filled by scheelite, the cavity then remaining being filled by quartz 14 VI. A and B, Thin sections of ore showing hamlinite (?), from Eagle Rock mine, 8 miles west of Boulder, Colo 15 VII. A, Wedge-shaped ferberite crystals from the Lone Tree mine, Neder- land, Colo.; B, Wedge-shaped ferberite crystals from the Hoosier mine, Nederland, Colo 18 VIII. A, Crystallized ferberite from the *'Crow patent," Nederland, Colo.; B, Crystallized ferberite from the Georgia A. mine, Nederland, Colo 19 IX. Crystallized ferberite with elongated rhombic crystal faces, from the Nugget mine, Gilpin County, Colo 20 X. Crystallized ferberite with elongated rhombic crystal faces, from the Nugget mine, Gilpin County, Colo. : A, Edge view; B, Side view.. 21 XI. Ferberite with rhombic crystal faces, from the Nugget mine, Gilpin County, Colo 22 XII. Very fine specimen of ferberite with rhombic crystal faces, from the Nugget mine, Gilpin County, Colo 23 XIII. A, Section of hiibnerite from the Dragoon Mountains, Ariz., showing zonal structures; B, Photomicrograph of granite from the Whet- stone Mountains, Ariz., showing wolframite with warty protuber- ances of scheelite along its edges 30 XIV. Section of wolframite from Irish Creek, Va., showing interstitial scheelite 31 ILLUSTRATIONS. 5 Pace. Figure 1. A, Orthographic projection of crystals with similar combinations, in parallel grouping, joined by the g (100) faces; B, Same with dis- similar combinations 41 2. Superposed crystals, joined by the q (001) faces 41 3. Long, narrow, wedge-shaped crystal of habit 1 67 4. Short, prismatic, somewhat flattened crystal of habit 2 57 5. Tabular crystal of habit 3 57 6. Cubic crystal of habit 4 57 7. Rhombic crystal of habit 5 67 8. Cleavage pieces of crystals 58 9. Striations on wedge-shaped crystals of habit 1 59 10. Crystal No. 4, wedge-shaped habit 59 11. Peculiar shape of wedge-shaped habit caused by cleavage 59 12. Crystal of short prismatic, somewhat flattened habit 59 13. Crystal of rhombic habit, nearly equidimensional 59 14. Contact twin on (023) 63 15. Contact twin on (023) 63 16. Line of contact of two contact twins 63 17. Penetration twin on (023) .' 64 18. Penetration twin on (023) 64 19. Crystal No. 29 64 20. Crystal No. 32 64 21. Crystal No. 33 64 22. Crystal No. 5 66 23. Crystal No. 6 66 24. Crystal No. 9 66 25. Crystal No. 13 66 26. Crystal No. 16 67 27. Crystal No. 17 67 28. CrystalNo.l8 67 29. Crystal No. 19 67 30. Crystal No. 20 68 31 . Crystal No. 36 68 32. Cubic crystal 68 33. Rhombic crystal 68 34. Crystal No. 26 68 35. Gnomonic projection of forms of the wolframite group 70 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. By Frank L. Hess and Waldemar T. Schaller. THE MINERAL RELATIONS OF FERBERITE. By Frank L. Hess. GEOGRAPHY AND PRODUCTION. Ferberite . as ordinarily defined, is that mineral of the wolframite series which is composed wholly or almost wholly of iron tunssliatfi^ and which, like other wolframites, crystalli zes in^the monocUnic sj[s^^ tem. It is comparatively rare and in most places where found it seems to occur in small quantities only. It occuj.s.inJ,arggst, quantity in Colorado^ about 25 miles northwest of Denver, mainl y in Bould er County, though ItEe' deposits extend a short distance southward beyond the county line into the north end of Gilpin County. From this area, which has a southwest-northeast length of about 12 miles and a width of 6 to 7 miles, an equivalent of probably 7,300 short tons of concentrates carrying 60 per cent WO3 had been mined from 1901, when exploitation of the tungsten veins began, to the close of 1912. The relative importance of the Boulder tungsten field, as the area is generally known, is indicated by the statistics of the production of tungsten ore in 1910, in which year the output of the field was 1,221 tons. In the same year the output of Queensland was 1,145 tons; Portugal, 1,132 tons; Argentina, 1,061 tons; and the world's production was probably about 7,500 tons, the remainder being smaller lots from manj countries.* The tungsten-bearing mineral produced from the three countries named was wolframite, and no other country produced any considerable quantity of ferberite. » Fof details see Hess, F. L., Tungsten: U. S. Geol. Survey Mineral Resources, 1910, pt. 1, p. 734, 1911. Since the above paragraph was written the world's statistics for 1911 and 1912 have become available, and these show that Burma has outstripped all other producers, its output of wolframite being equivalent to 2,095 short tons of orecarrying 60 per cent W0|. (Bee U. S. Oeol. Survey Mineral Resources, 1911 and 1912.) 7 8 COLOEADO FERBERITE AND THE WOLFRAMITE SERIES. CHARACTERISTICS OF THE FERBERITE. Ferberite occurs in the Boulder County field not only in large quantity, but in places in clean, beautifully developed crystals, and very commonly in small crystals coated with foreign material. The ferberite found over most of the field is jet black, but in a few places it is b ro w n^ It is opaque even in thin sections prepared for microscopic examination, and the clean crystals and cleavage faces are generally lustrous black. The ferberite of Boulder County is very resistant to weathering and forms placers which have been successfully worked. The fer- berite of the Black Hills (see analysis 81, pp. 32-33) decays, leaving a skeleton of hydrous iron oxide, and wolframites that are close to ferberite in composition decay similarly, but no alteration has been noted in the ferberite of the Boulder field, although it is in many places coated and discolored by hydrous iron oxide and other minerals. The other physical characteristics accord fairly well with those given by Dana ^ for the wolframites. The cleavage along h is per- fect, and in some specimens a parting is shown parallel to a, but I have not noticed the parting parallel to t (102) mentioned by Dana. The fracture is uneven and the mineral is brittle. Its streak and powder aie dark l)rown — nearly black — an^^ts Kardness is about^ Its specific ^av itv. as determined on selected crystals, is 7.499, ^ A splinter of pure material fuses to a globule which has a crystalline surface and is not magnetic. The brown mineral from the Rogers tract is almost infusible before the blowpipe, and is strongly mag- netic after heating. Although ferberite is not very soluble in acids, if it is finely pow- dered and boiled a few minutes with concentrated hydrochloric acid it gives a solution which, on the addition of zinc, readily shows a characteristic blue color, followed by the almost equally character- istic violet and brown. G«EOGRAPHY AND GEOLOGY OF THE BOUIiDER DISTRICT. Nederland, the commercial town of the Boulder tungsten field, lies 2 miles east of Cardinal station, on the Denver, Boulder & West- ern Railroad, and 4 miles north of Rollins ville, on the Denver, Northwestern & Pacific Railway. The ferberite-bearing area lies on an elevated plateau, above which, on the west, rise massive and imposing peaks. The altitude at N ederland is 8 ,237 feet. On the east an abrupt scarp descends from the plateau to the Great Plains. Streams draining the plateau have cut deep canyons extending back from the scarp to distances determined by the abrading power of the streams. 1 Dana, E. S., System of mineralogy, 6th ed., p. 983, 1909. OCCURRENCE, VEIN SYSTEMS, AND RELATIONS. 9 Biotite-homblende granite , in some places gneissoid, granitic crnflj^<;. ancl quartz-mjca schist form the country rocks. ^ The gneiss wnH ^^ ][yg|j pe o lder thar^E^^r anite, and all (lntc arc of pre^am- brian age and are cut by later dikes that raji<;( in composition Irom Tlmburgite to granite pegmatite. Dynamic metamorphism has in places made the granite, gneiss, and schist difficult to differentiate. Some of the dikes are also more or less squeezed. The gneiss is believed by R. D. George ^ and Edson S. Bastin^ to be of sedimentary origin. The pegmatites show only a Uttle crushing and carry few metallic minerals. OCCURRENCE, VEIN SYSTEMS, AND RELATIONS. The ferberite occu rs in a grc^up of veins whibh in general extcndn^ from southwost to northeast, though individual veins strike toward "neai'ly cvcmv point of the compass. On \]\o northwest and southwest si des of the tungsten-bearing area ^ are gold and silver bearing veins havuig the same gene ^*^| ti^<^p^ »-^ ^^p tungsten veins. The veins carrying the precious metals are acqntin- uation of the gold -bearing belt of Clear Creek and Gilpin counties.^ Two types of veins carry the gold and silver — those in which the minerals are mostly sulphides and those in which the gold occurs as a fftHnrj^ g^* The sulphidic veins are in general quartz veins carrying gold\nd silver bearing sulphides, such as pyrite, galena, chalcopyrite, and zinc blende. .. Silver predominates. The telluridic veins ^ occur in sheeted zones and contain only a little quartz. They carry gold mostly in a telluride, which is probably sylvanite, and the^ ^old pre- dominates over the silver. Pyrite, molybdenite, a vanadium mineral allied to roscoelite, barite, "aHularia, and chalcedony accompany the telluride . The veins are thin and commonly frozen to the walls. JThe ferberite veins are more or less connected with the gold veins, as miglil 1)0 expected from the general grouping, and theu- connection^ with the telluridic veins seems closer than with the sulphidic veins. Specimens from Magnolia, at the southeastern edge of the field^ showed both gold telluride and ferberite, but it could not be deter- mined which was the older. George reports a like specimen in which the telluride was evidently the older mineral." He also reports the occurrence of the two minerals in the Wheelmen Tunnel, in Boulder Canyon,** and at Sunshine, on the northern -^dge of the field. A speci- > George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey First Kept., pp. 19-20, 1909. « Oral statement. > Lindgren, Waldemar, Some gold and tungsten deposits of Boulder County, Colo.: Econ. Geology, voL 2, p. 453, 1907. * Idem, pp. 456-457. 5 Idem, pp. 457-459. « George, R. D., op. dt., p. 78. ' 10 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. men from Ward, still farther north and beyond the territory which up to this time has been productive, shows a wolframite which is prob- ably not f erberite and which occurs in long, slender crystals of a habit totally different from that of the f erberite of the main tungsten area. Embedded with this mineral in white quartz are pyrite and chalcopy- rite, apparently of the same general age, though the chalcopyrite is of later deposition, as it is pierced by the wolframite. The ore is said to carry both gold and silver. Although the data at hand are not very extensive, it seems probable that the connection between the three classes of veins may be fairly close and that there may not be a great difference in the ages of the several types. The manganese content of the tungsten mineral seems to increase somewhat progressively across the field from the Gilpin County line to Ward — that is, from south to north. A few miles south of the tungsten field in Gilpin County pitch- blende has been found in considerable quantity in close connection with gold and silver bearing veins, which lie in the same mineral belt. Forbes Rickard has recently noted ^ a close relationship between the ferberite veins of Boulder County and the pitchblende veins of Gilpin County. The ferb grite^X'gifis much resemble those carrying gold telluride. They occur in sheeted or crushed zones and ^e reticulated, the indi- vidual veins ranging from a small fraction of an inch to several inches jn thickness,^ while the ore-bearing body may reach a width of 14 feet, as in the Philadelphia mine of the Wolf Tongue Mining Co. The veins cut gran ite, gneiss, and pegmatite, and though the ore may extend from the granite into the gneiss it may be cut off at the contact, its continuity depending on local conditions, but there are only a few productive veins in the p;neiss» " -"-«*«- CHARACTERISTICS OF THE ORE. The amount and character of ganguc in the veins differ greatly in different parts of the field. Quartz, the universal vein mineral, occurs in much less quantity in the ferberite veins than in most veins. Only a very little visibly crystallized quartz in the ferberite veins lias come to my attention. There is, however, in most if not in all of the veins of the northeastern part of the field, and in many of the wider veins of the southwestern part of the field, a very fine gra ined gray or brown _C[uartz, known as ''bone," which has a fractur e much like that of chalcedony and which is largely a replacement of the country rock, .^ The ferberite in the northeastern half of the field appears to be less well crystallized than in the southwestern half. It occurs in some of the veins in minute particles mixed with quartz (see PL VI, p. 15), so lEat in many places the ore is difficult to concentrate, although the 1 Pitchblende from Quartz Hfli, Gilpin County, Colo.: Min. and Soi. Press, June 7, 1913, p. 852. U. 8. GEOLOGICAL SURVEY BULLETIN SSI PLATE I A. FERBERITE INCLOSING FINELY BRECCIATED GRANITE. From Rogers tract, Nederland, Colo. Natural size. B. "PEANUT ORE," FERBERITE INCLOSING FINELY BRECCIATED PEGMATITE. From the Conger mine, Nederland, Colo. Natural size. #^^1" CHARACTERISTICS OF THE ORE. 11 total percentage of WO3 may be as high as or higher than that in ores which are easily and profitably worked. In tho s()nt]i\v(Nt(Mii part of the field the narrower individual veins aremado up alinost wholly of ferberite, wEich has ^own from both sides of th<^ ('.r('vi('.(^s and f orms c onihs of small (r\'stals that coalesce at their bases. The combs are of fairly uniform thickness, so that although in the narrower crevices they may have met and grown together, in the wider cracks they form bristUng crusts of crystals on each side. In places these crystals are clean and bright but generally very smaU, from one to three thirty-seconds of an inch (1 to 2 milU- meters) across. Most of the crystals are covered with a coating of impure c haJcedony^jwhich in some specimens is mixed with opal and in othei -s contains much iron. The coating generally includes small , crystals of ferberite, which are of course of a latci- generation than those on the walls. Some vugs 3 or 4 inches across are entirely filled with such a mixture. On the Nugget claim, 3i miles southeast of Nederland, the crusts of nearly pure ferberite reach a thickness of more than an inch, and this claim has produced the finest crystaUized specimens of ferberite yet found. In the veins of this claim, as in the others, most of the crys- talUne aggregates are covered with a sihceous mixture, which here carries much brown iron oxide. The veins cut a moderately coarse grained pegmatite and have so far produced only a small quantity of ore. The Winnebago, an adjoining claim, has produced some small specimens of crystaUized ferberite from similar veins. In places the country rock instead of being sheeted is crushed into smaller, more nearly equidimensional fragments, which may not be over one-eighth inch (3 millimeters) in diameter. Ore in which frag- ments of rock no larger than half an inch (13 millimeters) across are embedded in ferberite is popularly know^n as ''peanut" or(\ from its resemblance to peanut candy. (See PL I.) Th<» fiagnuMits of the breccia vary greatly in size (PI. II), and where the fragments are larger the breccia is characterized by vugs lined with ferberite crystals. Both finely and coarsely brecciated ore is typical of the veins of the dis^rict^. Many of the veins have been opened several times, so that the ferberite Itself is ])i(U',(',iated. (See Pis. Ill and IV, B.) In places i]w fci Ix^rlte canlcs considerable manganese and grajd^ into wolfi aniitc. The mineral from Gordon Gulch carries almost 6 per cent MnO (analysis 58, pp. 30-31) and wolframite occurs on the norths _side of the field at Ward (analysis 49). The only other tungsten mineral so far identified in the field is scheelite . which occui-s in small quantity as a thin coating of octahedral nearly white crystals about one thirty-second inch (1 miUimeter) in thickness, over a film of fc y- j)erite covering the walls of cre^'ices in the Sugar Loaf district northern-central part of the area. Vugs in ore from the Frigid Mining 12 COLOKADO FERBERITE AND THE WOLFRAMITE SERIES. Co.'s claim at Crism an are lined with clear brownish and colorl^ scheehte crystals, the largest three thirty-seconds of an inch (2 milli- meters) ibluct. Vugs in ore from the Bogers tract, near the center of the area, are Hned with reddish-brown scheelite, which also occurs through the quartz in small quantity. Some of the vugs are of almost microscopic size. (See PI. V.) As seems to be usual in tungsten deposits, the scheelite formed later than the mineral of the wolframite series, but it is not a secondary mineral. In cleaning certain ferberfe i~ crystals with hydrofluoric acid deep pits with rather regular outlines are made, accompanied by the formation of yellow tungsten trioxide, and it seems possible that the pitting may be due to the removal of scheehte. MINERAIiS ASSOCIATED WITH THE FERBERITE. Associated minerals, other than quartz, are few and scarce in the ferberite veins of the main part of the field. Near the gold-silver bearing areas there is of course a mixture of the minerals of the several vein groups. The following minerals accompany ferberite in the veins : Adularia . — Adularia forms a coating one-sixteenth of an inch (2 millimeters) thick on the walls of the Black Hawk No. 2 vein, IJ [^{jfi^i miles south of Nederland. It is beneath most of the ferberite, but ijt^tfrf/ was probably deposited with the first of the ferberite. Adularia in microscopic grains is found in many of the veins. Calcite. — The gangue in the Conger mine carries microscopic parti- cles of a carbonate, which is probably calcite. Chalcedony. — Chalcedony mixed with more or less opal and hydrous iron oxide coats crystals from many of the veins. Q^olco^yrite. — Chalcopyrite occurs at Ward in veins carrying some wolframite, which seems to approach ferberite in composition, though no analysis of the mineral is at hand. Galena . — George ^ reports the occurrence of galena and sphalerite in veins with ferberite near Magnolia. The galena is said to occur generally in minute cubes but in considerable quantity. Gold and silver. — Gold and silver are reported to occur in some of the ferberite veins other than those in which sylvanite is present^ In the ore seen which is said to be gold-bearing smaU quantities of sulphides ar e present and the ^old is probably associated with the pyri|||^ Hills 2 states that eight assays of concentrates gave an . average of 0.01 ounce of gold to the ton. Greenawalt^ gives three analyses of concentrates which carried silver in quantities of 1.2, 2.4, and 3.1 ounces to the ton. The speci- 1 George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey First Rept., p. 75, 1909. » Hills, V. G., Tungsten mining and milling: Colorado Sci. Soc. Proc., vol 9, p. 150, 1909. • Greenawalt, W. E., The tungsten deposits of Boulder County, Colo.: Eng. and Min. Jour., vol. 83, p. 951, 1907. .^ .^ CO bs OC c HI o U. S. GEOLOGICAL SURVEY BULLETIN 583 PLATE IV A. CUT AND POLISHED CRYSTAL OF BROWN FERBERITE. From Winnebago claim near Roll'msville, Colo. Shows spongy structure of theferberite, the pores of which are filled with hydrous iron oxide. X 78. B. BRECCIATED FERBERITE VEIN. From the Conger mine, Nederland, Colo. Both the black and the gray edging it are ferberite, the differ- ence in color being due to the orientation of the crystals. Natural size. CHARACTERISTICS OF THE ORE. 13 mens came respectively from Beaver Creek, Nederland, and Gordon Gulch. Tomblin ^ states that m the Logan mine at Crisman free gold is sometimes found with ferberite. The occurrence of small quantities of gold and silver in tungsten veins is fairly common, but in many if not most veins the precious metals, though of the same general period of vein, f ormaiigya, are nrobably of later deposition than the wolframite. Silver seems to occur in greater quantity with the wolframites thanj does gold, and gold in greater proportional quantity with scheelite,! but this can not be stated as an invariable rule. Hiibnerite is found near Pony, Mont., in quartz veins which have been worked for silver; in veins prospected for silver but not rich enough to work near Ellsworth, Mammoth district, Nye County, Nev. (the name hiibnerite was given by Riotte to the mineral from this place); at Butte, Mont. ,2 on the 300-foot level of the Gagnon mine, where hiibnerite " formed an oreshootof argentiferous material;" in the Birdie mine 4 miles east of Butte (of very light brownish-yellow color) ;^ with silver minerals in the Combination mine, Philipsburg, Mont.;* in the mines of Silverton, Colo.^ (wolframite also); and Tonopah, Nev.® Wolframite occurs with silver ore in the Tip Top mine. Tip Top district, near Columbia, Ariz.; in a prospect of A. C. Young's at Old Hachita, N. Mex.;^ in the Victorio district, N.Mex.;* in the Sonoma Range, 15 miles south of Golconda, Nev.; at Silver Mines, 10 miles southeast of Ironton, Mo.;' and on the Silver Comet and other claims southwest of Pioche, Nev. Wolframites are also found with deposits carrying more gold than silver in the South Homestake mine, White Oaks, N.Mex.;^^ gold quartz veins on Sheep Creek near Salmo, British Columbia; " and gold mines of Lead, S. Dak. ; and at Cave Creek, Ariz., auriferous pyrite occurs with ferberite. 1 Tomblin, M. B., Tungsten; history, occurrence, uses: Facts concerning tungsten mining in world's greatest Add, Boulder County, Colo.: Boulder County Metal Mining Association Bull. No. 3, 1912. 2 Weed, W. H., Geology and ore deposits of the Butte district, Mont.: U. S. Geol. Survey Pref. Paper 74, p. 80, 1912. See also, Pearce, Richard, The association of minerals in the Gagnon vein, Butte City, Mont. : Am, Inst. Min. Eng. Trans., vol. 16, p. 64, 1888. » Tomek, F., Tungsten in Montana: Min. World, vol. 28, p. 68, 1908. * Goodale,C.W.,and Akers, W. A., Concentration before amalgamation for low-grade partially decomposed silver ores, with notes on the geology of the Flint Creek mining district: Am. Inst. Min. Eng. Trans., vol. 18, p. 248, 1890. 'Ransome, F. L.,Areportontheeoonomic geology of theSilvertonquadrangle, Colo.: U. S. Gool. Survey Bull. 182, pp. 86-87, 256, 1901. • Eakle, A. S., The minerals of Tonopah, Nev.: California Univ. Dept. Geology Bull., vol. 7, 1912, p. 18. Prof. Eakle calls the mineral wolframite, but states '-some of them [the crystals] are exceedingly thin and almost transparent, with a deep-red color." This corresponds with a specimen in my possession and seems to indicate hiibnerite rather than wolframite. T Lindgren, Waldemar, and others, The ore deposits of New Mexico: U. S. Geol. Survey Piol. Paper 68, p. 336, 1910. « Idem, p. 292. •Haworth, Erasmus, A contribution to the Archean geology of Missouri: Am. Geologist, vol. l,pp. 294- 295, 1888. »o Graton, L. C, U. S. Geol. Sursey Prof. Paper 68, p. 180, 1910. See analyses 4 and 16, p. 24. " Walker, T. L., The occurrence of tungsten ores in Canada: Canadian Min. Inst. Jour., vol. 11, pp. 867-371, 1908; Reiwrt on the tungsten ores of Canada: Canada Dept. Mines, Mines Branch, p. 37, 1909. 14 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. In 1907 a lot of wolframite ore, weighing 1.1 long tons, from Ravens- thorpe. Western Australia, carried 66.2 per cent WO3 and yielded 5.3 ounces of gold.^ Examples might be multiplied but would add little weight. The im- portance of those given lies in their bearing on the genesis of tungsten, gold, and silver ores. In many places tungsten ores are closely con- nected with pegmatites or lie in the pegmatites themselves and are probably in nearly all places close to a magmatic source. The gold and silve r found in the deposits must be likewise near their place of origin. Of course, it is not to be argued that the absence of tungsten mmerals implies that the gold and silver may not be near a magmatic source, but .goldjad-Sitefir ^appear to accompany sihceous solutions much farther from their igneous source than do tungsten minerals. It seems probable that the tungsten minerals may be deposited from the hotter waters emanating from magmas, and silver and gold from the solutions after they have somewhat cooled. Hamlinif.e ( jj. — In sections cut for microscopic study from a speci- men obtained at the Eagle Rock mine many small, very light green fragments of a uniaxial, optically positive mineral were found. As determined by E. S. Larsen, its indexes of refraction are 6;=1.620± 0.003, £ = 1.630 ±0.003. Its birefringence is 0.010, but some basal sections show anomalous birefringence as though divided into seg- ments. It has a perfect basal cleavage and shows a slight zonal growth. The particles show a tendency toward square sections, and the optical properties suggest that the mineral belongs to the alunite- hinsdalite series. Although very small, the particles are numerous, forming perhaps 10 to 25 per cent of the bulk of this particular ore. (See PI. VI.) The gangue is ^'homy" quartz through which are dis- tributed particles of ferberite and certain other particles which are attracted by a magnet, probably magnetite, both of which occur in grains almost as small as the unknown mineral. An attempt was made to separate the mineral from its gangue by grinding it very fine and passing the powder through a Thoulet solution of 2.8 specific gravity, but the material was too much mixed with quartz to show sufficient improvement for analytical purposes. The fact that with the at- tached quartz it sank through the liquid indicates that its specific gravity is above 2.8, but it is probably not over 3. A partial analysis by George Steiger, in the chemical laboratory of the United States Geological Survey, showed the presence of aluminum, 2 per cent strontium, a very little sulphur as a sulphate, and 3.6 per cent phos- phorus pentoxide. The only heavy metals found were tungsten, iron, manganese, and a trace of titanium. Fluorine and chlorine were absent. There was only a questionable trace of calcium and a very small quantity of magnesium. 1 Simpson, E. S., and Gibson, C. G., The distribution and occurrence of the baser metals in Western Australia: Western Australia Geol. Survey Bull. 30, pp. 115-117, 1907. I U. S. GEOLOGICAL SURVEY BULLETIN 683 PLATE VI .-' » ^ A|^^ f% » •i^^ /3 .X ^ A. ;^"r'^ftiL*^^^ -/. . ' *4i" I Mi ! n ' if ;m ii w> ^' --sk B. THIN SECTIONS OF ORE SHOWING HAMLINITE. From Eagle Rock Mine, 8 miles vi/est of Boulder, Colo. Groundmass, quartz. Mineral with high relief, hamlinite(?) Black mineral, ferberite. X 380. CHARACTERISTICS OP THE ORE. 16 The minera l seems to bo close t o hamlinite. for which the formula, as recalculated by Ihw/'^is 2Sr().3.\l203.2P205.7H20, but as a little sulphur is present it probably belongs In the series between hamlinite and svanbergite (2SrO.3Al2O3.P2O5.2SO3.6H2O). Another mineral of the same group, hinsdahte (2PbO.3Al2O3.P2O5.2SO3.6H2O), was discovered in 1010 by Larsen ^ as a vein mineral in the Golden Fleece mine, near Lake City, Colo. The same mineral has been found in sections from other parts of the Boulder field, though not in such large quantity as in the Eagle Rock specimen. Sections of ' 'hornstone " ore from other places have shown none of it. Howevor. pliosphorus in small quantity is nearly if not quite a universal conipuiieiit of the Boulder County tungsten ores,^ Hugh F. Watts, who has assayed thousands of samples of ferberite ores and concentrates coming from all parts of the Boulder field, states that whenever he has tested for it he has found phosphorus present.^ In one test on a composite of seven ores the phosphorus present amounted to 0.038 per cent. Hills* notes from 0.01 to 0.02 per cent phosphorus in eight out of nine analyses of concentrates and a trace in the other. Greenawalt ^ notes 0.05 per cent in a concentrate from Gordon Gulch. No apatite or other phosphate except the hamlinite (?) has been found, and it seems reasonable to suppose a very wide distribution of the hamlinite (?). The min- eral apparently occurs only in the quartz gangue, and if the ore is finely ground before separation very little will be left in the con- centrates, for its specific gravity (more than 2.8 and probably not higher than 3) is so low that it would readily pass into the tailings. I hope to make further investigation of this mineral. Hematite (specular). — At the south end of the Black Hawk No. 1 ve'in, li HUHS y^UflTol Nederland, a short vein w hich is nowhere more than a fe w inches thick, the ferberite gives way to specular hematite. This mineral is also found in small quantity in soinc other veins, and what is known as the May vein, a short distance east of the Black Hawk No. 1 vein, is a series of anastomosing veinlets made up of spec- ular hematite, which is said to be accompanied by a Httle tungsten, though none could be found in specimens collected. Hills * gives an analysis of ferberite concentrates from ''the east side of the dis- trict,'^ in which the content of FeO exceeds that of WO3, and another in which the quantity of FeO is only a Httle less than that of WO3. i'he analyses follow. 1 Prior, G. T., Hamlinite, plumbogummite (hitchoockite), beudantite, and svanbergite, as membenof a natural group of minerals: Mineralog. Mag., vol. 12, p. 253, 1900. « Larsen, E. S., and Schaller, W. T., Hinsdalite, a new mineral: Am. Jour. Sci, 4th ser., vol. 32, p. 251, 1911. * Private communication. < Hills, v. G., Tungsten mining and milling: Colorado Sci. Soc. Proc., vol. 9, p. 149, 1909. s Greenawalt, W. E., The tungsten deposits of Boulder County, Colo.: Eng. and Min. Jour., vol. 83, p. 951, 1907., 16 COLORADO FEEBERITE AND THE WOLFRAMITE SERIES. Analyses of tungsten concentrates treated at the Clarasdorf mill, near Boulder, Colo. Tungsten oxide.. Iron oxide Iron sulphide Sulphur Manganese oxide. Phosphorus Silicon dioxide... 38.46 39.31 .51 .27 3.10 .01 18.61 34.01 2.59 1.38 2.67 .01 22.13 The first analysis indicates a wolframite of the composition MnW04, 26 per cent; FeWO^, 74 per cent— a composition close to that of the Gordon Gulch wolframite (analysis No. 58, p. 31). After satisfying the MnO present only 8.8 of the 39.31 per cent FeO given is required to combine with the WO3. The second analysis indicates a wolfram- ite of the composition MnW04, 22.7 per cent; FeWO^, 77.3 per cent. This composition requires for combination with WO3 only 8.7 of the 34.01 per cent FeO. The form in which the iron is present is unknown, but the possibihty that it maybe specular hematite is at once suggested by knowledge of the occurrences mentioned. The sulphur shown in the analyses indicates, of course, that a small quantity of iron is pres- ent as pyrite. Occurrences of specular hematite with wolframites are not un- known. At South Crofty mine, Cornwall, ''the presence of specular iron has caused trouble in obtaining a high-class wolfram concen- trate.''^ It seems probable that deeper workings on the Rogers tract may show specular hematite, to the decomposition of which may be due the brown color of much of the ferberite from that tract. Limonite. — Limonite, under which term are here included all hy- drous oxides of iron, occu rs in , ma ny veins^ and nearly all the ore on the Rogers tract, about 2 miles northeast of Nederland, is stained brown with it. The crystals of ferberite are not only brown on the outside, but when broken show brown sections. (See p. 38 and PI. IV, A, p. 13.) The origin of the limonite and its relationship to the ferberite are unknown, but in part at least it is possibly altered from specular hematite, as already stated. Iron-bearing carbonates occur in some tungsten deposits, notably the scheelite deposits of Atoha, Cal. Carbonates decompose much more easily than specular hema- tite, and one may have been originally inclosed in the ferberite of the Rogers tract and some other places. Magnetite. — Magnetite is recorded by George ^ as occurring with the ferberite. Magnetite seems to be a probable associate of ferberite, 1 Anon., Cornwall (editorial): Min. Mag., London, vol. 8, p. 165, 1913. » George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey First Kept., p. 75, 1909. I CHARACTERISTICS OF THE ORE. 17 but in several specimens of powdered ferberite examined I have not been able to separate it with a horseshoe magnet nor to find it by microscopic examination with reflected light in polished and etched specimens from the Western Star and Nugget claims. In the ore from the Eagle Rock mine , however, a small quantity of magne^JQ^ material which is probably magnetite was ioun dT* Molvhdenite. — George* and Lindgren^ report, though Lindgren doubtfully, that molybdenite occurs with the ferberite in Boulder Coimty. I have not seen this association. Molybdenite is a com- mon assoc iate of wolfraniito in Queojislaiul •' and is also found witli it in Saxony '^ncTlEngland,* but the association is rare in this country, though molybdenite occurs with wolframite and tourmahne on the Black Horse claims, 10 miles southeast of Daisy, Stevens County, Wash., and in small quantity with ferberite at Cave Creek, Ariz. Opal. — Opal mixed with chalcedony and a httle hmonite forms a thin opaque yellowish-gray coating on ferberite crystals in the Black Hawk No. 1 vein, IJ miles south of Nederiand, and is probably a constituent of the sihceous coating on the ferberite from other mines. Fyritc. Pyrite is rare, except where the ferberite veins approacli the gold and silver veins, though here and there a little may be found. ^t one place in the Conger mine a vein of pyrite 2 inches thick cut across the ferberite veins. Iron sulphide in quantities reaching 3.25 per cent ® is indicated by analyses of concentrates from a number of places, as noted under hematite. .Quartz. ^(^m\v\z occurs in all veins in comparatively small quantity. ^ In most places it is so finely granular that it has a fracture hke chal- cedony, Verv httle of it shows crystal form. ScheeMte . — For discussion of the occurrence of scheehte see pages 11-12. SpJialerite. — Sphalerite is noted by George (see Galena, p. 12), and Moses ^ states that he found small yellow crystals upon ferberite specimens from the Boulder field. Sylvani te. — As has been noted, sylvanite occurs with ferberite at Ma gnolia. George® also notes this association in the vem^'s^ose^T by the Wheelmen Tunnel in the lower part of the canyon of Boulder Oeek and in a mine near Sunshine. » George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey First Rept., p. 75, 1909. » Econ. Geology, vol. 2, p. 461, 1907. * Cameron, W. E., Wdfram and molybdenite mining in Queensland: Queensland Ged. Survey Rept. 188, 13 pp., 1904. * Beck, R.jUber ein kiirzlich aufgeschlossenes Wolframerzgangfeld und einige andere neue Auiischliisae in sachsischen Wolframerzgruben: Zeitachr. prakt. Geologle, vol. 15, pp. 38,40, 1907. « Finlayson, A. M., The ore-bearing pegmatites of Carrock Fell and the genetic significance of timgsten ores: Geol. Mag., vol. 7, pp. 19-28, 1910. • Hills, V. G., Tungsten mining and milling: Colwado Sci. Soc. Proc., vd. 9,p. 149, 1909. T Moses, A. J., The crystallization of luzonite and other crystall(^raphic studies: Am. Jour. Sci., 4th ser., vol. 20, p. 282, 1905. • Op. cit., p. 76. 35659°— Bull. 583—14 2 18 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. SPECTROSCOPIC EXAMINATION OF THE FERBERITE. I Scandium/ columbium, tantalum, and other rare elements are Ifoimd in some wolframites, and a specimen of ferberite from the Con- 'ger mine was sent with a specimen of scheehte to Prof. G. Eberhard, Potsdam, Germany, who kindly made a spectroscopic analysis of them. In a letter dated August 20, 1912, to Adolph Knopf, of the United States Geological Survey, Prof. Eberhard says: The examination of the two minerals from Mr. Hess gave the following results: The lines of Ba, Gl, Pb, Ga, K, Li, Na, Ni, Ag, Sn, Bi, Zn, and Zr are absent in both minerals. The lines of the following elements are present in ferberite: Al, visible. Mo, weak?. Ca, weak. Sc, weak. Cr, weak or absent. Si, strong. Fe, strong. Sr, weak. Cb, weak. Ti, weak. Cu, weak. V, weak. Mg, visible. W, strong. Mn, weak. Y, absent. I have not sought for the elements not here listed. Lines marked "weak " indicate that the content of the element is small or very small. Lines marked " visible ' ' indi- cate that the content of the element is fairly large. Lines marked "strong " indicate that the content of the element is large. The element whose presence I could not substantiate with absolute certainty I have marked with a question. The content of scandium is certainly smaller than 0.005 per cent and is therefore chemically not detectable. Since this determination was made an article by H. S. Lukens^ jhas appeared, in which he describes the extraction of scandium [from residues of Colorado tungsten ores that had been treated by the ■General Electric Co. at Schenectady, N. Y. Lukens found 0.05 per cent of scandium oxide in the residues. In reply to my inquiries the Primos Chemical Co., which had furnished the ores, wrote, under date of April 18, 1914: - Regarding the scandium found in some of our ores, we have not yet located the point from which the ores come, but as a rule our residues contain no scandium. A great many tests are made right along. As we are getting ores from a great many points on our property, it is very difficult to tell from which particular openings they came. Most Boulder County ores contain no scandium. Have given samples right along to various universities, including the University of Pennsylvania, and though exhaustive tests have been made, not one of them has found any scandium. Another letter, dated April 27, 1914, says: As far as our records show, we shipped, with the probable exception of one small lot from Arizona, only Boulder County ores to the General Electric Co. tNo tungstic ocher, muscovite, stibnite, bismuth minerals, fluorite, tourmahne, axinite, cassiterite, or topaz — minerals which in some places occur with wolframite deposits, particularly if closely connected with pegmatites — are known to have been found in the Boulder field. 1 Winter Herbert, Ueber Vorkommen und Reindarstellung des Scandiums: Inaugural-Dissertation, Friedrich-Wilhelms-Universitat zu Berlin, pp. 22-23 et al., 1911. See also Mennicke, Hans, Die Metallurgie des Wolframs, pp. Ill ct seq., 1911. » Scandium tn American wolframite: Am. Chem. Soc. Jour., vol. 35, pp. 1470-1472, 1913. 0. 8. QEOLOOICAL SURVEY BULLETIN 683 PLATE VII A. WEDGE-SHAPED FERBERITE CRYSTALS FROM THE LONE TREE MINE, NEDERLAND, COLO. Fan-shaped intergrowth m right center. Coated with annmoniunn chloride. X 2. Ji. WEDGE-SHAPED FERBERITE CRYSTALS FROM THE HOOSIER MINE, NEDERLAND, COLO. Fan-shaped intergrowth and twins in lower right center. Coated with ammoniunn chloride. X 2. U. S. GEOLOGICAL SURVEY BULLETIN 583 PLATE VIII A. CRYSTALLIZED FERBERITE FROM THE "CROW PATENT," NEDERLAND, COLO. The crystals are attached by the C axis and show penetration twins and reentrant angles. Coated with ammonium chloride. Natural size. 1 s wm^^mm^ 4 ^^ ' * If w^' AaT 1" ' ^v* . ■■•1 HPS^^^^^^^K ^H V 1^ I w^ IV '•'V'-J'. i f '■»--^ \ ^^- 4 -=3^ 1 i?. CRYSTALLIZED FERBERITE FROM THE GEORGIA A. MINE, NEDERLAND, COLO. Coated with ammonium chloride. X 10. COLORADO FERBERITE AND THE WOLFRAMITE SERIES. 19 CRYSTAIililZED FERBERITE. As has been stated, the ferberitc^ coninionly ()cciij-> in (Icfiniio crystal forms and the beauTyof the crystals i> imiquo. However, although crystals are common, good speciniciis Miitable for display in museums are very rare, for most of the crystals are so small that they appear insignificant; they are very fragile and are easily broken in mininp:; and in many places they are coated with mixtures of cluilcodoiiy, opal, and hychous iron ()xi(l(^s in varvin,i: ])r()])()i-t ion^. This coating may be removed from some specimens without serious injury by treatment with hydrofluoric and sulphuric acids, but crystals so treated show uneven surfaces when an attempt is made to measure them with a goniometer. Probably a wedge shape is the commonest form of the crystals. This form occurs in many of the mines. One of the best specimens seen is from the Hoosier mine, between 1 and 2 miles northeast of Nederland (PI. YLl, B) . The wedge shapes are formed by the termina- tions at the ends of the h axis and most of the crystals axe attached at one end of this axis. Some crystals are intergrown in such a way SiS to produce a fan shape (PL \r[I, A and B). In a few specimens crystals attached by one end of the c axis are prominent, in which case the termination at each end of the h axis is shown. Some of the crystals show penetration twins, extending through c{001}. Around the penetrating crystal in two or three occurrences there seem to be reentrant angles in the penetrated members (PI. VIII, A). The speci- men illustrated came from a tract of land known as the Crow patent, near Nederland. In a specimen from the Greorgia A. claim the crystals are .almost cubic and about one one-hundredth inch (0.25 millimeter) across. Plate VIII, Bj represents the specimen magnified 10 diameters. Another form of crystal is found on the Nugget and the Winnebago claims, near RollinsviQe, Gilpin County. In this form the crystal presents a face (6) which is a long, narrow rhomb, with a length of about three-eighths inch (9.4 millimeters) and a width one-tenth to one-fifth as much. Typical specimens are shown in Plates IX and X. In some specimens the rhomb has sides much more nearly of equal length. (See PL XI.) Plate XII shows a very fine speci- men with peculiar, irregular faces. The crystal forms are described at length by W. T. Schaller in the latter part of this bulletin. COMPOSITION OF FERBERITE AND OTHER MEMBERS OF THE WOLFRAMITE SERIES. The^xiginal f erberite was found in the Sierra Almagrera, in southeru, Spain, and is stated by Liebe ^ to have been named by Breithaupt for K Ferber , of Gera. Liebe made an analysis of the mineral. (See^analysis No. 79, pp. 32-33.) 1 Liebe, K.L.H., Ein neuer Wolframite, ein Beitrag zu Mineral Cbemie: Neues Jahrb., 1S63, pp. 540-563. 20 COLOBADO FERBERITE AND THE WOLFRAMITE SERIES. The next year Rammelsberg ^ published an article on ferberite with an analysis of his own material (see analysis No. 82) from the same locality as that described by Liebe. He quotes Liebe's analysis and shows that the iron oxide and tungsten trioxide are not in a simple ratio and that there is an excess of iron oxide. Neither mineral was pure, and the analyses are not very satisfactory, so that calculation of iron in excess is uncertain, for it was probably present as an impurity and not as a part of the mineral. Liebe deducted 1.39 per cent limonite from his analysis. It seems certain that the calcium present should be calculated as scheelite, for scheelite almost always if not invariably accompanies otBer^ tun gsten materials. It is not visible in all specimens to~tHe unaided eye, but microscopic examination generally shows it as inter- stitial, inclosed in the wolframite crystals, filling vugs, or occurring separately in the deposit. (See PL V, p. 14, and PI. XIII, A and B, p. 30.) Some magnesium was found, but this element is not known to be a constituent of tungsten minerals, although A. M. Finlayson^ gives an analysis of scheelite from Donaldsons, New Zealand, containing 0.2 per cent MgO, which. he considers to be combined with WOg, taking the place of CaO, and Damour ^ considered that both calcium and magnesium might take the place of iron or manganese in wolf- ramite. That magnesium takes the place of either calcium or iron m tungsten minerals seems to me altogether unlikely. If it did so, some pure tungsten mineral — that is, some mineral which could be shown by microscopic or other examination not to contain par- ticles of other substances — would probably be found in which the magnesium would form a considerable part of the mineral, just as do those elements known to form natural tungstates — namely, calcium, copper, iron, lead, and manganese. Therefore, in recalculating these and other analyses on pages 24-35, neither magnesium nor calcium has been considered as belonging to the wolframite. To obtain a basis for differentiating ferberite from the remainder of the woKramite group all the analyses of wolframites (by which term is meant all members of the iron-manganese tungstate series) available to the author have been collected for comparison. More than 300 analyses were examined, but of these some represented ores rather than minerals; in many the WO3 had been determined by difference, which amounts to little more than a guess; in some the figures gave evidence that either the analytical work was bad or that the material was so impure that no proper comparison of the results would be possible. Where several analyses of the same material were obtained, only one has been tabulated. 1 Rammelsberg, C. F., Uber die chemische Zusammensetsung des Ferberite: K. Akad. Wiss. Berlin Monatsber., Jahre 1864, pp. 175-176, 1865. 2 FInlayson, A. M., The scheelite of Otago: New Zealand Inst. Trans, and Proc, vol. 40, p. 112, 1908. 3 Damour, A., Sur le wolfram tantalif6re du d^partement de la Haute-Vienne: Soc. g6ol. France Bull., 2d sen, vol. 5, p. 108, 1848. U. S. QEOLOQICAL SURVEY BULLETIN 683 PLATE IX CRYSTALLIZED FERBERITE WITH ELONGATED R-^OMBC CRYSTAL FACES. From the Nugget mine, Gilpin County, Colo. Coated with ammonium chloride. Natural size. U. 8. GEOLOGICAL SURVEY BULLETIN 583 PLATE X CRYSTALLIZED FERBERITE WITH ELONGATED RHOMBIC CRYSTAL FACES. From the Nugget mine, Gilpin County, Colo. Coated with ammonium chloride. Natural size. A, Edge view. B, Side view. COMPOSITION OF FERBERITE AND OTHER MEMBERS OF SERIES. 21 The analyses have all been recalculated in order to bring them to a common basis on which they can properly be compared. To do this it has been assumed that the theoretically pure members of the wolframite series contain only the hiibnerite molecule, MnWO^; the ferberite molecule, FeWO^; or a combination of the two mole- cules. All analyses have been reduced to these simple forms. As scheeUte, the calcium tungstate,. CaWO^, almost universally \ accompanies the wolframites, the lime indicated in the analyses has been considered to be a component of scheeUte unless data given with the analysis showed it to belong to some other mineral, such as fluorite. As the CaO is an impurity, it has therefore ordinarily been satisfied with WO3 and then discarded with all items other than FeO, MnO, and WO3. Of course, this scheme probably leads to error in certain of the analyses, as the lime in some may be derived from other sources than scheeKte, but these sources can not all be known, and as a general rule the process just described seems warranted. As a ppli.ed to the Boulder field in particular there can be little objec- tion^ as lime-bearing minerals other than scheelite are unconmion, Calciferous feldspars seem to occur in very few places, calcite is rare, and no other lime minerals have been noted in the veins. The analyses have been arranged in a series of decreasing MnWO^ j and increasing FeW04 content, so that the series begins with the! hubnerites and ends with the ferberites. This has determined the order of calculation, for the natural procedure has been t o satisfy first the !MnO with WO 3 and then to combine the remaining WO3 with so much of llie FeO as it would take up. Arbitrary or casual reasojpis are not the only bases for this mode of calculation, however, for man- ganese is much less common as an impurity in wolframites than is iron. " "The quantity of MnWO^ and FeWO^ obtained as a result of the operations has then been treated as the theoretically pure wolframite present in the substance analyzed, all other substances present being considered as impurities. From the theoretical wolframite as a basis have been computed the percentages of WO3, FeO, MnO, FeWO^, and MnW04 of which it is composed. In making the calculations the following atomic values and molec- ular ratios have been used : Atomic weif ht. Calcium 40 Iron 56 Manganese 55 Oxygen 16 Tungsten 184 Molecular ratio. WO, 232 ^ ^^ WO, 232 FeO ~ 72 WO, _ 232 MnO-TT ^'^^ 3.22 The values of the atomic weights are used only to the nearest integer and the ratios to the second decimal. These values are as 22 COLORADO FERBEEITE AND THE WOLFRAMITE SERIES. exact as are warranted by the errors due to the uncertainty of the constituent minerals of the analyzed material and to the faults of analysis. As an example of the process of calculation, analysis 37 may be taken: Analysis of wolframite from Hill City, S. Dak. Tungsten trioxide (WO3) 71. Ferrous oxide (FeO) 14. 3 Manganous oxide (MnO) 10. 2 Lime (CaO) 0. 7 Silica (SiOz) 2. 9 Magnesia (MgO) None. Water (H2O) 0. 3 99.4 WO3 CaO CaO W0» 0.7 X 4.14 = 2.9 CaO WO3 CaW04 0.7+2.9 =3.6 WO3 MnO MnO WOi 10.2 X 3.27 = 33.4 MnO WO3 MnWO* 10.2 + 33.4 = 43.6 WO3 required to satisfy the CaO and MnO 36. 3 WO3 in analysis 71. Less quantity for CaO and MnO 36. 3 WO3 to be satisfied by FeO 34. 7 WOs WO3 FeO re- quired to satisfy re- mainder of WO3. 34.7 4- 3.22 = 10.8 WO, FeO FeW04 34.7 + 10.8 = 45.5 FeO in analysis 14. 3 FeO required 10. 8 Excess of FeO 3.5 Adding the MnWO^ and FeWO,, Hiibnerite (MnWOJ 43. 6 Ferberite (FeW04) 45. 5 Theoretical wolframite in the material analyzed 89. 1 U. 8. QEOLOOICAL SURVEY BULLETIN 883 PLATE XI FERBERITE WITH RHOMBIC CRYSTAL FACES. From the Nugget mine, Gilpin County, Colo. Coated with ammonium chloride. Natural size. COMPOSITION OF FERBERITE AND OTHER MEMBERS OF SERIES. 23 Recalculating to percentages of the theoretical wolframite and then breaking up into oxides, Hiibnerite (MnWOJ 48. 9=11. 5 MnO+37. 4 WO, Ferberite (FeWOJ 51. 1=12. 1 FeO +39. WO, Total WOs in theoretical wolframite 76. 4 The presence of water (0.3) in the analysis probably indicates that a part of the apparent excess of FeO (3.5) is limonite. The 0.3 per cent of water will combine with 1.6 per cent of FeO to form 2.1 per cent of Umonite, considered as 2Fe303.3HjO. Tliis still leaves an excess of 1.9 per cent FeO. Summarizing, the calculation shows the wolframite to have a com- position of — W0» ^«-*l 'PeWO, 51.1 76.41 12. ij or \i 11. sj " Sio::::::::::::::::;"" --• " ^**"^«' "" With which is associated in the mass scheeUte, CaWO^, 3.6; excess FeO, 1.9; Umonite, 2.1. 24 COLOKADO PERBEEITE AND THE WOLFRAMITE SERIES. Analyses of minerals of Locality. Original analysis. Mo. WO3. FeO. MnO. CaO. Si02. MgO. Other sub- stances. Total 1 hObnerite. Philipsburg, Mont 74.82 75.58 74.28 75.45 74.88 74.12 70.21 71.50 74.32 74.75 75.12 76.63 75.94 74.46 75.36 76.33 76.50 76.61 0.06 .24 .47 .55 .56 1.42 2.03 5.40 2.11 2.91 3.01 1.61 2.38 3.29 2.66 3.82 4.40 4.64 25.00 23.40 22.73 23.31 23.87 23.21 21.72 23.10 20.90 21.93 20.54 21.78 21.57 19.90 19.50 19.72 18.50 18.59 99.88 100.02 99.69 100. 51 99.61 ? Ouray County, Colo.. 0.13 .02 .32 .14 0.62 1.33 .48 "b'.m None. .08 61)266?, 0.05... M0O3, trace... (CbTa)205?... CuO,0.08 3 4 Emerald, Nova Scotia White Oaks, N. Mex 5 Nye County, Nev. . fi Morococha, Peru 7 Silverton, Colo .37 4.91 Al2O3,0.56.... 99.80 100.00 98.91 99.70 99.71 100.11 99.90 99.87 "io6."66' 100.30 100.21 8 Schlaggenwalde, Bohemia Bayevka, Russia q 1.30 .11 1.04 .09 .28 in North Star mine, Colo Lawrence County, S. Dak Cement Creek, Colo Trace. 11 1? Trace. 13 Patterson Creek Idaho Sunday Gulch, S. Dak Dragoon Mountains, Ariz Bonito Mountain, N. Mex Oroville, "Wash S, 01 14 15 16 1.05 '""."i3" .20 .17 .42 1.70 .70 Trace. None. .20 Ignition, 0.75.. Undet.,0.78... 17 18 Bayevka, Russia 1. Hubnerite from Philipsburg, Mont. Analysis by A. H. Low quoted from Richard Pearce by Hillebrand, W. F., Miscellaneous mineral notes; Contributions to the min- eralogy of the Rocky Mountains: U. S. Geol. Survey Bull. 20, p. 96, 1885. 2. Hubnerite from the Royal Albert vein, UncOmpahgre district, Ouray County, Colo. Hillebrand, W. F., Miscellaneous mineral notes; Contributions to the miner- alogy of the Rocky Mountains: U. S. Geol. Survey Bull. 20, p. 96, 1885. 3. Hiibnerite from Emerald, Nova Scotia. Johnston, R. A. A., Hubnerite: Can- ada Geol. Survey Ann. Rept., new ser., vol. 11, p. lOR, 1898. 4. Hubnerite from the South Homestake mine. White Oaks, N. Mex. Analysis by J. G. Dinwiddie. Besides the items given the analysis showed HjO at 110° C, none; H2O above 110° C, 0.40. This hubnerite is to the unaided eye as black as the ferberite of the Boulder field, but in thin section it is translucent brown and olive- green. The streak is olive-green. Microscopic examination showed no scheelite but much fluorite, so that the calcium has been considered as derived from that mineral. See also analysis 16. 5. Hubnerite from Riotte's original locality, Ellsworth, Mammoth district, Nye County, Nev. Genth, F. A., Contributions to mineralogy, No. 52; with crystallo- graphic notes by S. L. Penfield: Am. Jour. Sci., 3d ser., vol. 43, p. 187, 1892. 6. Hiibnerite from Morococha, Peru. Analysis by Pfiiicker quoted by Domeyko, Ignacio, Mineralojla, vol. 2, p. 92, 1897. 7. Hubnerite from the Natalie mine, Silverton, Colo. Ekeley, J. B., Some Colorado tungsten ores: Min. World, vol. 30, p. 280, 1909. 8. Hiibnerite from Schlaggenwalde, Bohemia. Rammelsberg, C. F., Handbuch der Mineralchemie, p. 309, 1860. Fine red brown needles, with fluorspar and apatite. 9. Average of two analyses of hubnerite from Bayevka, Ural Mountains, Russia. Koulibin, Von N. v., Manganhaltiger Wolfram aus der Grube Bajewsk am Ural: Russ.-k. mineral. Gesell. St. Petersburg Verb., vol. 3, 2d ser., p. 3, 1868. 10. Hiibnerite from the North Star mine, Silverton, Colo. Genth, F. A., Contribu- tions to mineralogy, No. 52; with crystallographic notes by S. L. Penfield: Am. Jour. Sci., 3d ser., vol. 43, p. 186, 1892. COMPOSITION OP PERBERITE AND OTHER MEMBERS OF SERIES. 25 the wolframite aeries. No. Recalculated analysis. Specific gravity. WOj. FeO. MnO. FeWOi. MnWOi. Excess FeO. Excess MnO. CaW04. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.6 76.5 76.6 76.6 76.5 23.4 23.4 23.4 23.4 23.4 23.4 23.4 23.4 23.2 22.6 22.0 21.8 21.8 21.7 20.7 1&.9 18.9 18.8 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.2 96.8 94.0 93.3 93.1 92.8 88.4 85.1 80.9 80.2 0.1 .2 .5 .6 .6 1.4 2.0 6.4 1.9 2.3 1.2 .1 .8 1.7 .1 .3 2.1 .5 0.7 .1 7.177 .2 1.2 .5 .7 1.2 .7 1.9 6.45 0.2 .8 1.4 1.6 1.6 1.7 2.8 3.5 4.5 4.7 0.8 3.2 6.0 6.7 6.9 7.2 11.6 14.9 19.1 19.8 6.7 .6 5.4 .5 7.357 6.713 6.891 4.4 4.1 .7 1.0 1.0 7.163 Excess WO,. 1.7 .1 7.20 7.267 11. Hiibnerite from the Comstock mine, Lawrence County, S. Dak. Headden, W. P., Mineralogical notes: Colorado Sci. Soc. Proc, vol. 8, p. 175, 1906. "A black mineral fairly well crystallized." 12. Hubnerite from Cement Creek, Silverton, Colo. Genth, F. A., Contributions to mineralogy, No. 52; with crystallographic notes by S. L. Penfield: Am. Jour. Sci., 3d ser., vol. 43, p. 186, 1892. 13. Hubnerite from the Idaho Tungsten Co.'s property in the Blue Wing district, on Patterson Creek, Lemhi County, Idaho. An unpublished analysis by J. E. Talmadge, communicated by J. G. Lind. It seems improbable that from these deposits a specimen could be selected, the analysis of which would show neither SiO^ nor CaO, but this is of course surmise. In the analysis given, were the ordinary error of high MnO made, it might account for the good summation, were other elements undetermined. On the other hand, manganese oxides occur in the vein in some quantity (see Umpleby, J. B., Geology and ore deposits of Lemhi County, Idaho: U. S. Geol. Survey Bull. 528, pp. 3, etc., 1913), and it may well be that they are present in interstices of the hubnerite, part of which is so dark as to suggest the inclusion of either manganese or iron oxides. 14. Hubnerite from Sxmday Gulch, near Hill City, S. Dak. Headden, W. P., Mineralogical notes: Colorado Sci. Soc. Proc, vol. 8, p. 176, 1906. "Granular, almost entirely free from admixed gangue" (p. 175). 15. Hubnerite from Dragoon Mountains, Ariz. Guild, F. N., The mineralogy of Arizona, p. 92, 1910. 16. Hubnerite from Bonito Mountain, near White Oaks, N. Mex. Genth, F. A., Contributions to mineralogy, No. 52; with crystallographic notes by S. L. Penfield: Am. Jour. Sci., 3d ser., vol. 43, p. 187, 1892. 17. Hubnerite from Oroville, Wash. R. C. Wells, of the U. S. Geol. Survey, analyst. SiOj includes any other insolubles. Ta, Cb, Sn, Mo, and rare earths are not present in appreciable quantities. 18. Average of two Mialyses of hubnerite from Bayevka, Ural Mountains. Beck, W., and Teich, N., Ueber Wolfram und Scheelit aus Fundorten Russlands: Russ.-k. mineral. Gesell. St. Petersburg Verb., 2d ser., vol. 4, pp. 315-316, 1869. 26 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. Analyses of minerals of Locality. Original analysis. Mo. WO3. FeO. MnO. CaO. SiOa. MgO. Other sub- stances. Total. 19 WOLFBAMITE. Whetstone Mountains, Ariz.. Zinnwald, Germany 74.20 76.20 76.50 73.60 73.45 75.62 75.44 76.01 75.84 75.68 75.99 76.34 75.62 72.80 74.84 74.90 73.93 7L90 71.00 74.86 5.15 5.60 10.30 11.20 9.05 9.55 9.64 9.81 9.20 9.56 9.62 9.61 8.73 11.44 10.81 10.60 12.97 15.29 14.30 13.45 18.09 17.94 12.20 15.75 15.35 14.85 14.90 13.90 14.56 14.30 13.96 14.21 12.17 12.08 12.55 12.80 11.60 10.64 10.20 11.02 1.95 99.89 99.74 100.10 100.55 100.00 100.02 99.98 100.91 99.60 99.54 100.05 100.16 }l00.99 100.00 100.38 100.10 99.53 "'99.' 46" 100.55 90 ?1 1.10 Trace. 81162, trace... 9,?. Zinnwald (Germany?) LakeCouchiching, Ontario... Zinnwald, Germany 23 ?4 .20 Cb205?,1.95... ?5 Altenberg, Germany Tfi Zinnwald, Germany 1.19 ?7 ?8 Schlaggenwalde, Bohemia — Ziimwald ( Germany?) Zinnwald, Germany ?9 .48 80 31 do Tenasserim, Burma 2.27 1.18 .80 .30 /Ti02l.89 \H2O,0.31 T^ss,0.14 (Ta,C!b) 205,0.26 PbO, trace?... Ta2O6,1.03.... Undet., 1.15.. H2O,0.30 Cb203, 1.22.... 3? 2.36 .30 .■90 ■".■i2' Trace? S*^ Cornwall, England. 34 Lost River, Alaska 3'i Vilate, France 36 Sudzukoya, Japan '".'76' 1.02 2.90 None. 37 Hill City, S. Dak 38 Sierra Cordoba, Argentina... . 19. Wolframite from the Whetstone Mountains, 12 miles south of Benson, Ariz. Analysis by J. M. Ruthrauff quoted by Guild, F. N., The mineralogy of Arizona, p. 94, 1910. 20. Wolframite from Zinnwald, Germany. Bernoulli, F. A., Ueber Wolfram und einige seiner Verbindungen : Poggendorf's Annalen, 4th ser., vol. 21, p. 604, 1860. 21. Wolframite from Zinnwald, Bohemia. Helmhacker, R., Wolfram ore: Eng. and Min. Jour., vol. 62, p. 154, 1896. 22. Wolframite from Zinnwald (Germany?). Richardson, T., Analysis of wolfram: Thomson's Records of general science, vol. 1, p. 451, 1835. 23. Wolframite from Lake Couchiching, Ontario. Hunt, T. S . , Analysis of Canadian wolfram: Canadian Jour., new ser., vol. 5, p. 303, 1860. 24. Wolframite from Zinnwald, Germany. Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen des Wolframmetalles: Jour, prakt. Chemie, vol. 42, p. 97, 1847. 25. Wolframite from Altenberg, Germany. Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen des Wolframmetalles: Jour, prakt. Chemie, vol. 42, p. 110, 1847. 26. Wolframite from Zinnwald, Germany. Schneider, R., Ueber die chemische Constitution des Wolframminerals: Jour, prakt. Chemie, vol. 49, p. 332, 1850. 27. Wolframite from Neubeschert-Gliick, Freiberg, Germany. Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen des Wolframmetalles: Jour, prakt. Chemie, vol. 42, p. 102, 1847. 28. Wolframite from Schlaggenwalde, Bohemia. Kemdt, T., Ueber die Krystall- form und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbind- ungen des Wolframmetalles: Jour, prakt. Chemie, vol. 42, p. 109, 1847. 29. Wolframite from Zinnwald, Germany (?). Ebelmen, J. J., Note sur la com- position du wolfram: Annales des mines, 4th ser., vol. 4, p. 407, 1843. 30. Wolframite from Zinnwald, Germany. Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen des Wolframmetalles: Jour, prakt. Chemie, vol. 42, p. 96, 1847. COMPOSITION OP FERBERITE AND OTHER MEMBERS OF SERIES. 27 the wolframite series — Continued. No. Recalctilated analysis. Specific gravity. WO». FeO. MnO. FeWO«. UnWO*. Excess FeO. Excess WO,. CaWO*. 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 76.5 76.6 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.5 76.4 76.4 76.4 76.4 76.4 4.8 5.4 6.4 7.1 7.5 8.5 8.6 8.7 8.7 9.1 9.1 9.3 9.4 9.9 10.1 10.3 11.6 12.1 12.1 12.3 18.7 18.0 17.1 16.4 16.0 15.0 14.9 14.8 14.8 14.4 14.4 14.2 14.1 13.6 13.4 13.3 12.0 11.5 11.5 11.3 20.3 23.0 27.1 30.1 31.5 35.8 36.3 36.6 37.3 38.3 38.4 39.2 39.8 41.9 42.7 43.3 48.8 50.9 51.1 61.9 79.7 77.0 72.9 69.9 68.5 64.2 63.7 63.4 62.7 61.7 61.6 60.8 60.2 58.1 67.3 56.7 51.2 49.1 48.9 48.1 0.5 .2 4.6 4.3 1.9 1.2 1.2 1.7 .4 .6 .8 .3 .5 2.6 1.9 .7 1.8 4.0 1.9 1.4 6.7 7.017 7.230 7.198 6.1 7.229 7.535 2.5 11,7 6.1 4.1 1.5 7.272 7.000 («) 3.6 a Limonite 2.1 per cent. 31. Wolframite from Zinn,wald, Germany. Weidinger, G., Analyse eines Wol- framkrystalls aus den Gruben bei sa- hsisch Zinnwald an der bohmisch-sachsischen Grenze: Zeitschr. Pharm., vol. 7, p. 73, 1855. 32. Wolframite presumably from the property of the Mount Pima Mining Co. (Ltd.), Tenasserim, Lower Burma. A published analysis by O. Burger furnished through the courtesy of Radcliff & Co., Rangoon, Burma. 33. Wolframite from Cornwall, England. The exact locality of origin is unknown. Analysis by Edgar T. Wherry on specimen No. 80179 in the United States National Museum. The analysis, which will appear in the Proceedings of the Museum, showed, besides the items given: FcaOg, 0.70, which was calculated to its equivalent of FeO and added to that item. The wolframite is black and opaque and occurs in large crystals with pyrite and chalcopyrite. A section showed a later deposition of very thin bands of scheelite and wolframite in cracks of the crystals, so that the CaO evi- dently should be calculated into scheelite. 34. Wolframite from Lost River, Alaska. R. C.Wells, of the U. S. Geol. Survey, analyst. No Ta, Cb, Mo, or rare earths present. 35. Wolframite from between Vilate and Chanteloube, France. Damour, A., Sur le wolfram tantalif^re du d6partement de la Haute-Vienne: Soc. g^l. France Bull., 2d ser., vol. 5, p. 108, 1848. 36. Wolframite from Takatori mine, Takatori Mountain, near Sudzukoya, Higashi- Ibaraki County, State of Hitachi, Japan. The mine is 12 miles northwest of Mito and 14 miles northeast of Kasama. Analysis by S. Katsuno, personal communication, Nov. 30, 1912. 37. Wolframite from Black Metal claims, Hill City, S. Dak. R. C. Wells, of the U. S. Geol. Survey, analyst. Any AI2O3 present is included with the FeO. 38. Wolframite from the southern end of the Sierra Cordoba, Argentina. Boden- bender, G., Die Wolfram-Minen der Sierra von C6rdoba in der Argentinischen Re- publik: Zeitschr. prakt. Geologie, Nov., 1894, p. 409. 28 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. Analyses of minerals oj Locality. Original analysis. Mo. WOa. FeO. MnO. CaO. SiOo. MgO. Other sub- stances. Total. 39 WOLFRAMITE— continued. Lead, S. Dak 61.70 76.21 70.38 73.47 74.78 51.00 64.13 75.07 74.43 75.56 71.27 76.14 73.46 57.18 9.18 12.87 13.88 15.13 13.80 20.20 10.88 15.61 16.90 16.22 20.01 15.67 16.90 15.87 8.21 10.52 9.52 9.81 9.36 6.07 6.42 8.24 8.37 8.42 7.15 8.34 6.97 5.30 0.93 '"2."i6' .54 Trace. "'i.'2i" .52 12.87 .15 Trace. . 99.64 99.75 100. 70 100.05 100.12 40 Montebelleux, France Sadisdorf, Germany 41 42 do Tavoy, Burma 43 .30 L83 7.71 Trace. "i.'lh' .31 Cb2O5,0.20.... As, 3.82 44 Wheal Gorland, Cornwall. .. . Northwest Rpalri. . . . 4,') SnO2,0.68 Cb203, 1.12.... 99.89 100.87 99.70 100.20 100.01 100.15 100.02 46 47 Quebrada de la Viuda, Argentina. Miramichi River, New Brunswick. Altai, Siberia 48 49 Ward, Colo L68 fiO Felsobany a, Hungary Perilhao, Portugal Wheal Gorland, Cornwall. . . . 51 2.69 6.83 52 . . ... As, 2. 39 39. Wolframite from Two Strike mine, Yellow Creek, Lead, S. Dak. W. F. Hille- brand, analyst. Irving, J. D., Economic resources of the northern Black Hills: U. S. Geol. Survey Prof. Paper 26, p. 167, 1904. Besides the items noted, the analysis showed: FegOg, 3.85; AI2O3, 0.52; SrO, 0.02; BaO, 0.04; KaO+NagO+LigO, 0.08; H2O, below 105° C, 0.20; HgO above 105° C, 0.87; AsgOg, 1.25; P2O5, 0.12; traces of V2O5 and S or SO3. Extremely minute traces of Zn, Cu, Sb, and Sn were also found. Assays gave: Gold 0.05 ounce and silver 0.25 ounce to the ton of 2,000 pounds. The P2O5 was probably combined with CaO as apatite, and 0.18 has therefore been deducted from the CaO before combining it with WO3 for scheelite. The FeO is not sufficient, as indicated by the analysis, to combine with the WO3, and 0.6 must be taken from the FejOg to supply the deficiency. A partial analysis of a specimen from the Harrison mine, near Lead, is given, as follows: SiOg, 9.60; WO3, 61.70; FcgOg and FeO, 12.67, MnO, 7.21; CaO, 5.39. Recalculated: WO3, 76.5; FeO, 9.5; MnO, 14.0; FeW04; 40.2; MnW04, 59.8; CaW04, 39.4. In this analysis the CaO (5.39) is high, and no de- termination of P2O5 is indicated. There is no corresponding increase in the WO3 and the relation of the FeO: MnO is so much different as to indicate that part of the lime probably belongs in apatite. Specimens of ore collected by the present writer from this general locality and examined microscopically show apatite in small quantity. As given, the analysis falls between Nos. 31 and 32. 40. Wolframite from Montebelleux, Brittany, France. Bourion, F., Sur un mode general de preparation des chlorures anhydres et ses applications h. I'analyse chimique: Annales chim. phys., 8th ser., vol. 21, p. 103, 1910. 41. Wolframite from the Kupfergrube, Sadisdorf, Germany. Winter, H., Ueber Vorkommen und Reindarstellung des Scandiums: Inaugural-Dissertation, Friedrich- Wilhelms-Universitat zu Berlin, p. 23, 1911. Besides the items mentioned, the analy- sis shows PO4, 2.23; M0O3, trace; earth acids (TaOa, TiOj), 2.07; PbO, 0.46; Sc, 0.2. It is stated that calcium phosphate was present in the gangue, and the CaO has there- fore been combined with the PO4, which it is hardly sufficient to satisfy. 42. Wolframite from the Kupfergrube, Sadisdorf, Germany. Winter, H., Ueber Vorkommen und Reindarstellung des Scandiums: Inaugural-Dissertation, Friedrich- Wilhelms-Universitat zu Berlin, p. 22, 1911. The analysis also showed: Ti02 and TaOj, 0.63; PbO and SnOg, 0.47; Sc, 0.2. 43. Wolframite from the Tavoy district, Lower Burma. Analysis by C. S. Fawcitt. Bleeck, A. W. G., On some occurrences of wolframite lodes and deposits in the Tavoy District of Lower Burma. India Geol. Survey Records, vol. 43, pt. 1, pp. 67-68, 1913. COMPOSITION OF FERBERITE AND OTHER MEMBERS OF SERIES. 29 the wolframite series — Continued. No. Recalculated analysis. SpecMo gravity. WO,. FeO. MnO. FeW04. MnW04. Excess FeO. Excess WO,. CaWO«. 39 40 41 42 43 44 45 46 47 48 49 50 51 52 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 12.8 13.0 13.2 13.4 14.0 14.5 14.9 15.0 15.0 15.1 15.1 15.2 16.3 16.6 10.8 10.6 10.4 10.2 9.6 9.1 8.7 8.6 8.6 8.5 8.5 8.4 7.3 7.0 64.1 64.8 55.8 56.4 59.2 61.0 62.8 63.2 63.3 63.6 63.8 64.3 69.0 70.0 45.9 45.2 44.2 43.6 40.8 39.0 37.2 36.8 36.7 36.4 36.2 35.7 31.0 30.0 4.0 0.2 1.7 3.0 .1 (?) 2.8 3.1 6.2 2.7 1.3 2.3 1.3 7.2 .5 1.2 .2 6.968 8.1 7.458 Besides the items noted in the table, the analysis shows AljO,, 0.81; BijOj, 0.14; SnOa, trace; M0O3, 0.51; HjO, 0.22. 44. Ore from Wheal Gorland, Cornwall. Analysis by B. Kitto, communicated by Mr. R. Woodward, managing director of Edgar Allen & Co. (Ltd.), Sheffield, England. The analysis also shows: Pb, 0.10; Mg, trace; Bi, 0.15; P, trace; CaFj, 4.06; Cu, 0.88; S, 2.02; AI2O3, 1.77; SnOj, 8.64; O, by difference, 3.96. Cu, Fe, S, and As were com- bined as nearly as possible to form chalcopyrite and arsenopyrite. Although not made on as pure material as might be wished for the purposes of this paper, the analysis shows approximately the composition of the wolframite. 45. Wolframite from northwest Spain (ore). Steinhart, O. J., Classification, occur- rence, identification, and properties of tungsten ores: Mineral Industry, vol. 17, p. 830, 1909. The analysis also shows: AI2O3, 5.32; and CrO, 0.38. 46. Wolframite from Quebrada de la Viuda, Department of San Xavier, Argentina. Bodenbender, G., Die Wolfram-Minen der Sierra von C6rdoba in der Argentinischen Republik: Zeitschr. prokt. Geologie, Nov., 1894, p. 409. A trace of CaO is pres- ent but no MgO. 47. Wolframite from the confluence of the southwest Miramichi and Burnt Hill Brook, New Brunswick. Walker, T. L., Recently discovered wolframite deposits in New Brunswick: Econ. Geology, vol. 6, p. 397, 1911. 48. Wolframite from Kolywanowschen mine, Altai, Siberia. Beck, W., and Teich, N., Ueber Wolfram und Scheelit aus Fundorten Russlands: Russ.-k. mineral. Gesell. St. Petersburg Verb., 2d ser., vol. 4, p. 317, 1869. 49. Wolframite from Ward, Colo. Analysis by J. B. Ekeley. George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey First Rept., p. 43, 1909. 50. Wolframite from Felsobanya, Hungary. Sipocz, L., Ueber die chemische Zusammensetzung einiger seltener Minerale aus Ungam: Min. pet. Mitt., new ser., vol. 7, p. 270, 1886. 51. Wolframite from Perilhao, Portugal. Bourion, F., .Sur un mode g^n^ral de preparation des chlorures anhydres et ses applications a I'analyse chimique: Annales chim. et phys., 8th ser., vol. 21, p. 104, 1910. 52. Ore from Wheal Gorland, Cornwall. Analysis by B. Kitto, communicated by Mr. R. Woodward, managing director of Edgar Allen & Co. (Ltd.), Sheffield, England. Fe (12.34) has been calculated as FeO (15.87). The analysis also shows: SnOj, 2.75; traces of Pb and MgO; CaFj, 4.37; Cu, 0.45; S, 1.31; AljO,, 4.13; and O, by differ- ence, 2.95. 30 COLOEADO FERBEKITE AND THE WOLFRAMITE SERIES. Analyses of minerals of Locality. Original analysis. No. WOj. FeO. MnO. CaO. SiOj. MgO. Other sub- stances. Total. 53 WOLFRAMITE— continued. Meymac, France 74.75 74.25 76.00 76.24 71.2 60.84 75.79 76.21 70.73 74.56 76.57 75.73 75.82 75.90 76.02 16.17 15.85 17.00 16.39 18.0 18.36 19.80 18.54 16.42 15.19 18.98 18.68 19.33 19.25 19.21 6.40 6.51 6.60 6.05 6.0 4.73 5.35 5.23 4.71 3.84 4.90 4.93 4.84 4.80 4.75 0.40 .80 .20 1.05 .32 .40 .50 4.10 .70 1.12 ""."90' 4.0 16.28 0.17 .04 None. .11 TajO5,0.95.... fH2O,0.70 \Ta2O5,1.10.... 99.96 } 99.25 100.70 99.84 } } 101.26 100.74 97.08 100.20 101. 15 99.92 99.99 99.95 99.98 54 55 do Oreville, S. Dak... 56 Carrock Fell, England Mount Carbine, Queensland.. Gordon Gulch, Colo 57 /Bi,0.1 \Cu,0.2 fS,0.20... \P,0.05 Sn02, trace.... W Cabarrus County, N. C Neudorf, Germany 60 '".'26" '"".'se" .36 .14 .41 Trace. 61 Pioche, Nev (Ta,Cb)2O5,0.82 (Ta,Cb)205,etc., 0.96. 6? Irish Creek, Va 63 Stassberg, Germanv 64 Cedar Canyon, Wash Undet.,0.22... 65 66 Harzgerode, G ermany Montevideo 67 53. Wolframite from Meymac, Correze, France. Camot, A., Sur quelques min^- raux de tungst^ne de Meymac (Correze): Compt. Rend., vol. 79, p. 638, 1874. Any alumina present is included with the silica. 54. Wolframite from Meymac, Correze, France. Carnot, A., Sur quelques min6- raux de tungst^ne de Meymac (Correze): Compt. Rend., vol. 79, p. 638, 1874. 55. Wolframite from "Wolfram" claim, 3 miles east of Oreville, S. Dak. R. C. Wells, of the U. S. Geol. Survey, analyst. SiOj includes any other insolubles. Ta, Cb, Sn, Mo, and rare earths are not present in appreciable quantities. 56. Wolframite from Carrock Fell, England. Finlayson, A. M., The ore-bearing pegmatites of Carrock Fell and the genetic significance of tungsten ores: Geol. Mag., vol. 7, p. 21, 1910. 57. Wolframite. Analysis of "typical Mount Carbine [Queensland] wolfram con- centrate" by Alex. Cumming. The SiOg (4.0) includes "insol., etc." Besides the items in the table there is also "undetermined, 0.5." Quoted by Ball, L. C, Wol- fram mines of Mount Carbine. No. 1: Queensland Govt. Min. Jour., vol. 14, p. 70, 1913. 58. Ore from Gordon Gulch, Boulder County, Colo. Greenawalt, W. E., The tungsten deposits of Boulder County, Colo. : Eng. and Min. Jour., vol. 83, p. 951, 1907. The analysis also includes: Gold, trace; silver, 3.1 ounces to the ton. The item given under SiOa is given by Greenawalt as "Si." 59. Wolframite from the Flowe mine, Cabarrus County, N. C. Genth, F. A., The minerals of North Carolina: U. S. Geol. Survey Bull. 74, p. 80, 1891. 60. Wolframite from Grube Pfaffenberg, Neudorf, Harz Mountains, Germany. Schneider, R., Ueber die chemische Constitution des Wolfram-Minerals: Jour, prakt. Chemie, vol. 49, p. 334, 1850. 61. Black wolframite from Silver Comet mine, 11 miles west of Pioche, Nev. J. G. Dinwiddle, analyst; personal communication. The analysis also showed FejOg, 2.92; H3O below 110° C, 0.03; HgO above 110° C, 0.57. The FeO of the analysis gave an U. 8. OEOLOOICAL 8URVEV BULLETIN B8S PLATE Xni ^ A. HUBNERITE from the dragoon mountains, ARIZ. Section showing zonal structure. X 5. B. PHOTOMICROGRAPH OF GRANITE FROM WHETSTONE MOUNTAINS, ARIZ. Showing wolframite (black) with warty protuberances of scheelite. X 90. U, S. GEOLOGICAL SURVEY BULLETIN 583 PLATE XIV WOLFRAMITE FROM IRISH CREEK, VA. Section showing interstitial sclieelite. X 30. COMPOSITION OF FERBERITE AND OTHER MEMBERS OF SERIES. 31 the wolframite seriet — Continued. No. Recalculated analysis. Specific gravity. WOs. FeO. MnO. FeWO<. MnWO«. Excess FeO. Excess WO,. CaWO«. 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.4 76.3 76.3 76.3 76.3 76.3 76.3 16.6 16.9 16.9 17.2 17.2 17.7 18.1 18.3 18.3 18.6 18.6 18.7 18.8 18.9 18.9 7.0 6.7 6.7 6.4 6.4 5.9 5.5 5.3 5.3 5.1 5.1 5.0 4.9 4.8 4.8 70.1 71.4 71.4 72.6 72.5 74.6 76.6 77.2 77.4 78.3 78.3 78.8 79.2 79.4 79.6 29.9 28.6 28.6 27.5 27.5 25.4 23.4 22.8 22.6 21.7 21.7 21.2 20.8 20.6 20.4 0.4 .1 .4 .2 2.0 4.3 2.1 .6 2.8 1.2 1.1 .2 .7 .5 .4 4.1 2.1 I.O 5.4 6.70 1.7 2.1 3.3 21.1 3.6 7.496 7. si 7.228 7.513 excess of 0.2 and to this has been added 2.6, the equivalent of the FejOj given. In appearance the material is so pure that it is difficult to account for the apparent presence of 3.3 per cent of scheelite (CaW04). Possibly the "H2O above 110° C, 0.57," should be CO2. 62. Wolframite from Cash tin mine, Irish Creek, Rockbridge County, Va. Analysis by J. G. Dinwiddie. The analysis also shows FeaOg, 4.03; FeO, 11.56; HjO at 110°, 0.12; H2O above 110°, 0.63; TiOg, 0.02; AlA* 0.32; CO2, 0.5. The FejOg has been changed to FeO and added to that item. It is extremely difficult to make accurate determinations of ferric and ferrous iron in the wolframites, owing to the likelihood of part of the iron being oxidized during grinding and difficulties inherent in the chemical determination. The change also makes the analysis foot up better. The scheelite (CaW04) is very high, (21.1), but specimens of wolframite from the locality show many inclusions of scheelite. (See PI. XIV.) 63. Wolframite from Neuhaus Stollberg, Stassberg, Harz Mountains, Germany. Analysis by Petzold. Schneider, R., Ueber einen harzer Wolfram: Poggendorf's Annalen, 4th ser., vol. 3, p. 474, 1854. 64. Wolframite from the Germania mine. Cedar Canyon, Stevens County, Wash. R. C. Wells, of the U. S. Geol. Survey, analyst. 65. Wolframite from Chanteloube, Limoges, France. Kemdt, T., Ueber die Krys- tallform und chemische Zusammensetzung der natiirlichen undkunstlichen Verbind- ungendes Wolf rammetalles : Jour, prakt. Chemie, vol. 42, p. 105, 1847. 66. Wolframite from Harzgerode, Germany. Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen desWolframmetalles: Jour, prakt. Chemie, vol. 42, p. 105, 1847. 67. Wolframite from "Monte Video," country not given, Kemdt, T., Ueber die Krystallform und chemische Zusammensetzung der natiirlichen und kiinstlichen Verbindungen des Wolf rammetalles: Jour, prakt. Chemie, vol. 42, p. 102, 1847. 32 COLORADO FERBEKITE AND THE WOLFRAMITE SERIES. Analyses of minerals of No. Locality. Original analysis. WO3. FeO. MnO. CaO. SiOo MgO. Other sub- stances. Total. FERBERITE. Limoges, France Traversella, Italy Nagpur, India Estremadura, Spain Inverell. New South Wales Neudon , Germany Torrington, New South Wales Gordon Gulch, Colo Neudorf, Germany Beaver Creek, Colo Cave Creek, Ariz Sierra Almagrera, Spain Kootenay Belle mine, British Columbia. HUl City, S. Dak Sierra Almagrera, Spain Adun-Tschilon, Siberia Ivigtut, Greenland Last Chance, Colo 76.20 75.99 61.59 72.93 77.64 76.30 70.73 61.80 76.28 66.41 73.74 70.11 74.90 70.94 69.06 75.55 75.19 62.30 19.19 16.29 14.50 22.70 18.76 20.12 18.13 16.36 20.38 24.31 18.18 23.29 17.75 17.61 25.97 21.31 22.97 19.90 4.48 3.45 2.94 4.10 4.12 4.12 3.64 3.12 3.80 3.25 3.37 3.02 2.75 2.71 2.17 2.37 L33 0.80 3.40 P, 0.018. .38 L64 .35 .20 15.93 .16 Trace. 1.71 .07 Gangue, 6.55., AljOs, 1.06... .24 1.75 1.52 .42 1.02 8.70 fS,0.02 (P. trace (Ta,Cb)2O5,2.20 Cb205, trace... 100.67 99.76 72.45 99.73 100.52 101.08 99.69 100.33 100.73 L52 .26 .79 14.68 CbjOs, 0.76 . AI2O3I.34. 99.79 99.90 100.60 99.96 98.72 100.00 100.25 99.70 68 . Ferberite from Limoges, probably from Puy-les-Vignes. (See Lacroix, A . , Mineral logie de la France et de see colonies, vol. 4, pt. 1, p. 285, footnote, 1910.) Ebelmen, J. J., Note sur la composition du wolfram: Annales des mines, 4tli ser., vol. 4, p. 407, 1843. 69. Ferberite from Traversella, Italy. Bernoulli, F. A., Ueber Wolfram und einige seiner Verbindungen: Poggendorf's Annalen, 4tli ser., vol. 21, p. 603, 1860. 70. Ferberite from Nagpur district, India. Analysis by Carnegie Steel Co. Quoted by Fermor, L. L., Note on an occurrence of wolfram in the Nagpur district, Central Provinces: India Geol. Survey Records, vol. 36, pt. 4, p. 309, 1908. 71. Ferberite from Estremadura, Spain. Analysis by Truchot quoted by Mennicke, Hans, Die Metallurgie des Wolfram, p. 18, 1911. 72. Ferberite from Inverell, County Gough, New South Wales. Liversidge, A., The minerals of New South Wales, p. 85, 1888. 73. Ferberite from Grube Meiseberg, Neudorf, Harz Mountains, Germany. Schnei- der, R., Ueber die chemische Constitution des Wolfram-Minerals: Jour, prakt. Chemie, vol. 49, p. 334, 1850. 74. Ferberite from the Bismuth mine, Torrington, New South Wales. Analysis by H. P. White quoted by Came, J. E., The tungsten mining industry in New South Wales: New South Wales Geol. Survey Min. Res. No. 15, p. 70, 1912. 75. Ferberite from Gordon Gulch, Boulder County, Colo. Analysis quoted as having been made by the Colorado Tungsten Corporation. George, R. D., The main tungsten area of Boulder Coxmty, Colo.: Colorado Geol. Survey First Rept., p. 43, 1909. 76. Ferberite from Grube Meiseberg, Neudorf, Germany. Schneider, R., Ueber die chemische Constitution des Wolfram-Minerals: Jour, prakt. Chemie, vol. 49, p. 334, 1850. 77. Ore from Beaver Creek, Boulder County, Colo. Analysis given by Greenawalt, W. E., The tungsten deposits of Boulder County, Colo.: Eng. and Min. Jour., vol. 83, p. 951, 1907. The analysis also gives: Gold, trace; silver, 1.2 ounces to the ton. The item given under SiOj is designated in the original as "Si." 78. Ferberite from Cave Creek, Maricopa County, Ariz., U. S. Nat. Mus. catalogue No. 87283. Analysis by Edgar T. Wherry. The mineral is black and opaque. The COMPOSITION OF FERBERITE AND OTHER MEMBERS OP SERIES. 33 the wolframite aeries — Continued. No. Recalculated analysis. SpeciAo gmvity. WO,. FeO. MnO. FeWO<. ItnWOi. Excess FeO. Excess WO,. 0aWO4. 68 69 70 71 72 73 74 75 76 n ?l 80 81 82 83 84 85 76.4 76.4 76.4 76.4 76.3 76.3 76. ,35 76.3 76.4 76.3 76.3 76.3 76.3 76.3 76.3 76.3 76.3 76.3 19.1 19.2 19.3 19.3 19.4 19.5 19.7 19.8 19.8 19.9 20.0 20.0 20.5 20.5 21.0 21.3 22.3 22.8 4.5 4.4 4.3 4.3 4.3 4.2 3.95 3.9 3.8 3.8 3.7 3.7 3.2 3.2 2.7 2.4 1.4 .9 80.8 81.1 81.5 81.7 81.8 82.1 83.1 83.4 83.6 84.0 84.2 84.3 86.4 86.6 88.7 89.6 94.2 96.1 19.2 18.9 18.5 18.3 18.2 17.9 16.9 16.6 16.4 16.0 15.8 15.7 13.6 13.5 11.3 10.4 5.8 3.9 0.1 1.4 1.5 4.2 • 20.7 3.7 1.1 2.0 .6 1.8 1.0 .8 .8 7.0 3.1 1.2 9.0 7.8 7.182 5.4 6.801 2.4 5.4 8.7 .6 1.0 2.3 7.8 1.3 7.169 6.405 7.334 4.1 analysis shows also CuO, 1.34; "TajOg, approximately 1.50, and CbjOj, 0.70, judging from density of oxides. " The quantity of tantalic and columbic pentoxides indicated is unusually high. The excess WO3 shown seems to be combined with part of the CuO to form a hydrous copper tungstate new to science. Work is now being under- taken on this mineral. Part of the copper is probably combined with the SiOj as chrysocolla. 79. Ferberite from the Sierra Almagrera, southern Spain. Liebe, K. L. T., Ein neuer Wolframit; ein Beitrag zur Mineral-Chemie: Neues Jahrb., 1863 p. 645,. The analysis also shows AI2O3, 1.15; limonite, 1.39; SnOj, 0.14; GIO, trace. The analysis Bs given follows Dana's recalculation after subtracting the limonite (System of Mineralogy, p. 985). The specific-gravity determination is stated to have been made by Breithaupt. 80. Ferberite from Kootenay Belle mine, Salmo, British Columbia. Walker, T. L., Report on the tungsten ores of Canada: Canadian Dept. Mines, Mines Branch, p. 38, 1909. 81. Ferberite from the American Tungsten Co.'s mine, BUU City, S. Dak. Analysis made at the South Dakota School of Mines. Quoted by C. H. Fulton in a private report on the mine. Traces of SnOj and S were found. If the quantities given are otherwise correct, it seems probable that a part of the substance determined as "SiOa " is really CaO; hence the excess of WO3. 82. Ferberite from the Sierra Almagrera, southern Spain. Rammelsbeig, C. F., Ueberdie chemische Zusammensetzung des Ferberits: K. preuss. Akad. Wiss. Ber- lin Monatsber., p. 175, 1865. 83. Ferberite from Adun-Tschilon, Siberia. Average of four analyses. Beck, W., and Teich, N., Ueber Wolfram und Scheelit aus Fundorten Russlands: Russ.-k. mineral. Gesell. St. Petersburg Verb., 2d ser., vol. 4, p. 315, 1869. 84. Ferberite from Ivigtut, Greenland. Analysis by Chr. Christensen. Boggild, 0. B., Mineralogia Groenland (Saertryke af Meddelelser om Gronland, vol. 32): Min- eral, and Geol. Mus. Univ. Copenhagen, Contr. to Mineralogy No. 6, p. 182, 1905. 85. Ferberite from Last Chance, Boulder County, Colo. Analysis by J. B. Ekeley. George, R. D., The main tungsten area of Boulder County, Colo.: Colorado Geol. Survey thirst Rept., p. 42, 1909. 35659°— Bull. 583—14 3 M COLORADO FERBERITE AND THE WOLFRAMITE SERIES. Analyses of minerah oj Locality. \ Oiigliialai^alysis. Ma wc ^ MnO. c»o. SIO* MgO. Other sab- sumoes. Total. M 1f«MliK.fMn 7LM 2I.» Mennicke, Hans, Die Metallurgie des Wolframs, pp. 125-130, 1911. * Damour, A., Sur le wolfram tantalif^re du d^partement de la' Haute-Vienne: Soc. g(k>l . France BulL, ^ ser., p. 108, 1848. 38 COLOKADO FEKBERITE AND THE WOLFRAMITE SERIES. Wolframite: A monoclinic mineral containing the ferberite mole- cule (FeW04) and the hiibnerite molecule (MnW04) in all propor- tions between 20 per cent FeWO^ and 80 per cent MnWO^, and 80 per cent FeW04 and 20 per cent MnW04. Under this scheme the analyses show ferberites from 13 widely separated localities — Boulder County, Colo., Cave Creek, Ariz., and Hill City, S. Dak., in the United States; British Columbia; Greenland; France; Saxony; Italy; Sierra Almagrera and Estremadura, Spain; New South Wales; India; Siberia; and Japan. The ferberite of Japan was described as reinite and replaces scheeHte. From Limoges, France (No. 68), is shown a ferberite that contains nearly the maxi- mum amount of manganese. The purest ferberite^ showing no manganese a nd only a small excess of iron oxide (0.8 per cent)'7is ^^°^ f{(MftJ"p^"^ Mnerals from Gordon Gulch (No. 58) and Ward (No. 49), in the Boulder tungsten field, fall well within the wolfram- ites, although from the most remarkable ferberite locality known. They merely emphasize the characteristic variability of the hiibnerite- ferberite mixture. EXCESS OF FERROUS OXIDE AND MANGANOUS OXIDE. ' A point to which considerable importance has been attached by different writers is the excess of FeO in the ferberites, but the table of analyses shows that they are not unique in this, though some ferberites do carry large excesses of FeO. The proneness of WO3 to form a lower oxide on heating and its solubility make it seem probable that many determinations of the oxide are low, so that the appearance of an excess of 0.1 or 0.2 per cent FeO may be neglected. It is also probable that in many of the analyses the MnO is too high, a common error when the determina- tion is made gravimetrically, and a very small excess of MnO would cause a somewhat larger apparent excess in the FeO. Only a few of the analyses show the presence of alumina, but many wolframites occur in a gangue containing muscovite or feldspar or both, and small quantities are likely to be mixed with the mineral analyzed. If the mineral is fused, the alumina, unless specially separated, will be precipitated with the iron oxide, and, if the iron is determined gravimetrically, will by so much make it appear larger. Iron oxide is commonly present as such, for in the oxidized zone the breaking down of minerals such as siderite, pyrite, chalcopyrite, or wolf- ramite setsfree iron oxide, which mayformfilms over the residual wolf- ramite or fill cavities of microscopic or larger size. A cut and polished crystal of brown ferberite from the Winnebago claim near Rollins- ville shows a very porous structure (see PL IV, ^; p. 13) and the cavities are coated with hydrous iron oxide. This material is similar to that found on part of the Rogers tract and would surely give a EXCESS OP FERROUS OXIDE AND MANGA'NOUS OXIDE. 39 considerable excess of iron on analysis. Specular hematite or magnetite, in particles too small to be easily distinguished, may occur in the ore, and the presence of one or both of these minerals may account for the surplus iron shown in some determinations. In those wolframites whicli contain tantalum and col unibiuin colum])i1(^ may fui-nis1i m ])nil of \]\o appaiciit cxcoss of iron. Micro- scopic examinations made hy icIlecU'd liglit on ])()nshe(l and etched specimens of clean black ferberite show none of the differences in texture to be expected if such other minerals were present. There are, however, minute cavities which may be partly filled with iron minerals. Manganese dioxide, though in less quantity than iron oxides, is commonly associated with the ores, but its presence on the lighter-colored hiibnerites should be easily distinguishable. The possibility of FeO and MnO being held in solid solution in the minerals of the wolframite series suggests itself, but no proof of this has been found. It is to be noted that if the analyses given had been recalculated by first satisfying the FeO with WO3, and then combining the remainder of the WO3 with the ^InO, the excess of the FeO would disappear in most of the analyses and there would be an excess of MnO. However, as just stated, manganese oxide occurs with the wolframites in much less quantity than iron oxide, and for this reason in recalculating an analysis it is best to first satisfy the MnO with WO3. It appears, therefore, that though some of the woLframitesI may carry an excess of FeO, and a few an excess of both FeO and! MnO, most if not all of the ap parent excesses are due to impurities] present in the material analyzea and to errors of anjiTysis. Many careful analyses of well-selected minerals and many examina- tions by metallographic methods must be made before a real excess of FeO or MnO in the wolframites can be demonstrated. CRYSTALLOGRAPHY OF FERBERITE FROM COLORADO. By Waldemar T. Schaller. PREVIOUS PUBLICATIONS. The several papers mentioned by Mr. Hess in his part of this report give some general facts in regard to the habit and size of crystals of ferberite. Two other papers, by Warren and by Moses (see Bibliog- raphy, pp. 74-75), give descriptions of ferberite crystals which may have come from this locahty. The crystal figured by Warren is said to have come from South Dakota, though he states that the exact locality could not be ascertained. From the appearance of the crystal it is more Ukely to have come from Colorado than from South Dakota. The crystal figured and described by Moses as crystallized wolframite from Boulder County, Colo., is very similar to those here described. These two papers are the only publications on the crystallography of the ferberite from Colorado that could be found. GENERAL CHARACTER OF THE CRYSTALS. MODE OP OCCUIIBENCE. In the specimens examined the ferberite crystals are perched on the country rock in groups or they fine or nearly fill the cavities or fissures in the matrix. Layers of ferberite several centimeters thick, consisting of crystals whose bases have coalesced, are found on the rock. Much of the ferberite, which at first glance seems to be mas- sive, is found on closer inspection to be a granular compact mass of small crystals. The crystals occur isolated as distinct individuals (Pis. VII, p. 18, and VIII, p. 19), in groups of parallel or nearly parallel individuals (Pis. IX, p. 20, and X, p. 21), or in confused masses consisting of numerous abutting and even penetrating crystals. Twins are com- mon, though single untwinned crystals are far more plentiful. The nearly parallel groupings are of two kinds: (1) A group of flattened crystals which may depart several degrees from strict parallehsm and which are joined by the a(lOO) faces (fig. 1); and (2) crystals joined by the c(OOl) faces and superposed, the fine of demarcation of the 40 GENERAL CHARACTER OF THE CRYSTALS. 41 (liflerent crystals being well shown by the irregular lines crossing the prism zone normal to the vertical striations (fig. 2). The distri- bution of the dome faces on several of the parallel groupings joined by the a (100) face conclusive- ly demonstrates that the crystals are not twinned. Well-developed crys- tals are abundant, but many crystals are rounded and curved either in a single zone or throughout. The curving of the sur- faces in a single zone is generally due to the marked development of the striations in the prism zone. (See fig. 9, p. 59.) The curving of the faces over an entire crystal is due to the nearly parallel grouping of a number of crystals, each one deviating successively a little more from parallelism with the original unit. The various forms of occurrence of ferberite found on the specimens examined may conveniently be summarized as follows : 1, Massive. 2, Bladed, indistinctly crystallized. 3, Distinct individual crystals. a, Single well-formed crystals (Pis. VII, VIII, XI, and XII, and text figs. 3-34). b, Twinned crystals (PL VIII,A, and textfigs. 14, 15, 17,andl8). c, Crystals grouped in parallel po- sition (Pis. IX and X). (1), Composition face a(lOO) (fig. 1). (2), Composition face c(OOl) (fig. 2). d, Rounded crystals or groups of crystals. SIZE. FiGXTBE 1 .—A , Orthographic projection of crystals with similar combinations in parallel grouping, joined by the a(lOO) face; B, Orthographic projection of two crystals with dissimilar combinations. The cleavage parallel to 6(0l0) in many crys- tals terminates one side. Forms: c{001}, 6{010}, g{100>, 7n<110}, /{210>. Figure 2.— Superposed crystals, joined by the c(OOl) faces. The line of demarcation is normal to the vertical striations on the large a(lOO) faces. In size the crystals vary considera- bly. The largest^ seen were about 1.5 c entimeters long (6 axis), half as high (c axis). an3 a l)out TrnilTr- gieters"tEicE^ TS"axis) . The general average would be aboutS to lOmilh- meters long, 2 to 5 millimeters high, and 1 to 3 millimeters thick. On 42 COLOKADO FERBERITE AND THE WOLFRAMITE SERIES. some of the rock specimens areas extending over many square centi- meters are coated by minute crystals, few of which measure more than a miUimeter in any direction. Most of the crystals measured were much smaller than the average. The dimensions of the crystals were accurately measured under the microscope, so that their proportions might be shown in the drawings for the text figures in this bulletin. Of 18 crystals thus accurately measured the a axis lay between 0.3 and 0.7 millimeter on 14 crystals; the h axis (which in most of these crys- tals has about half the true original value) between 0.5 and 2.5 milli- meters on 16 crystals; and the c axis between 1.0 and 3. 5 millimeters on 13 crystals. The extreme values are: a axis, 0.3 to 5.0 millimeters (the 5.0 is an extreme value, the next highest is only 1.5; all the other values are less than 1.0 millimeter); h axis, 0.6 to 3.2 milhmeters; c axis, 0.3 to 3.8 millimeters. Most of the crystals measured were bounded on one side by a cleav- age face of &(010), so that the sizes here given do not actually repre- sent the size of the original crystals in the direction of the h axis. In the illustrations (figs. 3 to 34) the crystals are generally shown rela- tively longer in the h axis than the measured values indicate, in order to represent more truly their actual original sizes. The h axis on many of the complete crystals was probably twice as great as measured. COLOR AND CLEAVAGE. The crystals are black and their luster is splendent, nearly metallic. The streak is dark brown, suggesting hematite. It is distinctly not JiTack . Cleavage is cllnopinacoidal, 5(010} , very good, and commonly visible on the basal pinacoid. THE MEASURED CRYSTALS BY LOCALITIES. In the following table the crystals measured are grouped according to the mine from which they came. In addition their general character and habit are given for reference. These descriptions and locahties are based entirely on the material collected by Mr. Hess. For other locahties, not mentioned here, the papers given by Mr. Hess in his bibHography should be consulted. AXIAL ELEMENTS. Lut of crystals by localities. 43 Crj'S- tal No. Locality. Illus- trated In figure — Orifcinal note- book No. Description and habit.o Crystals 1-12 from 1 specin^n of ore from the 100-foot level of the Hoosier mine, Boulder County, Colo. Crystals 13-17 from 1 specimen from the Nugpet i claim, 5 miles southeast of Nederland, IJ miles ' northeast of Rollinsville, Gilpin County, Colo. Specimen taken from a 17-foot winze. Crystals 18-23, 24-25, 26-27 , from three differen tspeci- ■ mens, all from the sam t claim as crystals 13-17 (Nugget claim). Crystals 28-35 from one specimen from Tovm Lot mine, Nederland, Boulder County, Colo. •From Black Hawk claim, Boulder County, Colo From Georgia A. vein, 2 miles northeast of Nederland, Boulder County, Colo. 24 Ai A, A, A4 As A« At As A, A 10 An A„ B, B, B, B4 Bs Ci-1 Ci-2 Ci-3 Ci-4 Ci-5 Ci-6 C^l C^2 Cs-l C3-2 Cr-3 Di D, D3 D4 Ds D« D; El E, 8, prismatic. 8, wedgelike. 8, prismatic. 8, wedgelike. 8, prismatic. Do. Do. 8, wedgelike. 8, prismatic. T, tabular. Do. Do. 8, prismatic. Do. Do. G, prismatic. 8, prismatic. Do. Do. G, prismatic. S, prismatic. Do. T, tabular. 8, rhombic. Do. Do. T, tabular. S, tabular. S, wedgelike. Do. Do. Do. Do. Do. Do. S, cubic. Do. Do. a S, simple crystal; G, group of crystals In nearly parallel position; T, twin crystal. , AXIAIi EIjEMENTS. f The discussion of the axial elements of ferberite leads at once to the question of the relation of ferberite to the wolframite group. In this connection a consideration of the relation in angidar values between the pure iron tungstate and the pure manganese tungstate is of interest. The ferberite crystals at hand did not yield results as satisfactory as had been expected, because of the imperfection of the crystals, due to striations, parallel groupings, and hke features; because of the scarcity of well-developed terminal forms; and because the high poUsh of most of the crystals had been destroyed by the hydrofluoric acid used to remove the matrix and clean the crystals. CALCULATION OP VALUES. Below are given the best measurements obtained that are suitable for the calculation of the axial elements, and these are compared with the measurements given in the literature for the members of the 44 COLOKADO FEKBEEITE AND THE WOLFRAMITE SERIES. wolframite group. All measurements were made with a Goldschmidt two-circle goniometer. Average of best measurements. (010) : (110) Fair reflection: 50° 16^ 22 23 12 24 20 22 16 15 Poor reflection: 50° 31^ 27 28 22 17 20 21 Average of 9 measurements with fair reflection, 50° 19^ Average of 7 measurements with poor reflection, 50° 24^ Average of the 16 measurement^/ 50° 20i^ (001) : (Oil) Good reflection: 41° 00^ 01 00 40 59 59 57 57 58 56 53 56 Average of 11 measurements, 40° 58''. Average of 4 measurements, 89° 37''. In the measurements of the prism angles the cj) angle was obtained, this being the same as the angle (010) A prism. The Vq or zero I Good measurements weighted twice as much as fair ones; fair measurements weighted twice as much as poor ones. (010) : (210) Good reflection: 67° 27^ 23 24 26 25 31 25 32 21 Fair reflection: 67° 17^ 23 16 28 19 27 30 26 Average of 9 measurements with good reflection, 67° 26^ Average of 8 measurements with fair reflection, 67° 23^ Average of the 17 measurements,^ 67° 25^ (001) : (102) 27° 46^ 49 27 43 45 37 50 Average of 6 measurements. 27° 46^ (001) : (100) 89° 50^ 34 32 33 AXIAL ELEMENTS. 45 reading on 6(010) was averaged for each crystal from the readings obtained on (010) and (010) (often a cleavage face), and from the aver- age of (110) and (iTO), and (210) and (2T0), respectively. The c(OOl) faces were generally striated in the zone (001) : (100), but this in nowise interfered with the accuracy of the measurement of the angle (001) : (Oil). The accurate measurements from (001) to (102) and to (100) were very few in number, as the base (001) was striated in this direction on most of the crystals. COMPARISON OF VALUES. Instead of deriving axial elements from these angular values I have compared the interfacial angles directly with the best ones I could find in the literature for the entire wolframite group. These have been arranged in order of decreasing percentage of MnO, so that the first lines in the table below represent hiibnerite and the last lines (except the very last) represent ferberite. The very last line contains the values taken from Goldschmidt's Winkel- tabellen, in which the axial elements of Descloizeaux, Krenner, and Seligmann have been averaged. (See Bibliography, pp. 74-75.) A careful study of the angular values given in any column does not show any regular increase or decrease correspondiug with the regular decrease in percentage of MnO. In fact the varia- tion in angular values for two or more wolframites of nearly the same composition is nearly as great as between the extreme end members. The correlation of the chemical composition and the crystallographic constants is doubtful in so far as the analytical figures given were not obtained on the material actually measured. Comparison of angles with variation in chemical composition. Locality and Author. Per cent MnO. Angle. material. (010):(110). (010):(210). (001):(011). (001):(lp2). (001):(100). MnW04 (arti- ficial). Megaba.'nte Groth and Arz- runi. ..do 23.4 22.24 21.93 9.4 4.96 4.84 3.15 !o 50 15 50 27i 50 06 50 21 50 30 50 18i 50 36 50 204 50 33 50 27 / Colorado Penfield.. 67 19 40 55 40 51^ 40 42J 40 57 41 03} 4058 27 12i 89 07} MnjFej (W04)5 (artificial). Saxony Groth and Arz- runi. Krenner. . . 67 36 67 28 67 40 67 25 27 29 27 27i 27 50i 27 46 27 33 27 35 89 m France Descloizeaux Seligmann W.T.Schaller.. Groth and Arz- runi. G 1 dschmidt's Winkeltabel- len. Spain. 89 34 Colorado FeW04 (arti- ficial). Average o 89 37 67 34^ 40 54 89 32 a Computed from axial elements of Descloizeaux, Krenner, and Seligmann. 46 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. A definite, measured difference in crystallographic constants be- tween ferberite (FeW04) and hiibnerite (Mn04) is not shown by the table just given. The average axial elements given by Goldschmidt represent closely the angular values for the different members of the wolframite group. These values are also close to those obtained on the Colorado ferberite as shown below. Comparison of angles of ferberite from Colorado with the values given in Goldschmidt' s Tables. Angle. Gold- schmidt's Winkel- tabellen. Boulder County ferberite. Difference. (010):(110) (010):(210)...,... (001):(011) (001):(102) (001):(100) 50 27 67 34 40 54 27 35 89 32 50 m 67 25 40 58 27 46 89 37 -06^ -09 +04 +11 +05 The axial elements given by Goldschmidt, namely, a: 6:^ = 0.8255: 1:0.8664, ^ = 89° 32', therefore best represent the constants for the entire wolframite group. The data for the percentages of manganese given in the table on page 45 have been taken from Dana.^ Descloizeaux's measurements were made on material from Vilate, near Chanteloube (Haute- Vienne), France. An analysis of wolframite from Chanteloube shows 4.84 per cent MnO and 19.32 per cent FeO. Krenner's measurements were made on crystals from Ehrenfriedersdorf , Saxony, and an analy- sis of material from the same locality shows 4.96 per cent MnO and 19.16 per cent FeO. Seligmann's ferberite from Sierra Almagrera, Spain, contains 3.15 per cent MnO and 19.95 per cent FeO, according to Doelter.2 Two confirmatory analyses of the Spanish ferberite show 3.00 and 3.02 per cent MnO with high FeO. Hiibnerite from Colorado^ showed 21.93 per cent MnO and 2.91 per cent FeO. ^'Megabasite" from Schlaggenwald contained 22.24 per cent MnO and 3.74 per cent FeO. FORMS AND ANGLES. A total of 32 forms were determined on the ferberite crystals from Colorado. Of these 12 are new for the wolframite group. These 32 forms are given in the table below with the measured and cal- culated coordinate angles. The new forms are marked with an asterisk (*). 1 Dana, E. S., System of mineralogy, 6th ed., p. 984, 1892. 2 Zeitschr. Kryst. Min., vol. 11, p. 348, 1887. 8 Penfield, S. L.; see Dana, E. S., op. cit., pp. 983, 984. NEW FORMS. List of forms and angles onferberite crystals. {New forms are marked with an asterisk.] No. Letter. Symbol. Measured. Calculated. Gold- Schmidt. MiUer. ^ fi * P o / O 1 e 1 1 1 c 001 90 00 23 90 00 028 2 b Ooo 010 00 90 00 000 90 00 3 a ooO 100 90 12 90 00 90 00 90 00 4 r oo2 120 33 49 90 00 31 12 90 00 5 m oo 110 50 21 90 00 50 27 90 00 6 I 2oo 210 67 25 90 00 67 31 90 00 7 *R Voo 15.7.0 69 00 90 00 68 56 90 00 8 *C |oo 940 70 01 90 00 69 51 90 00 9 *F |oo 520 71 39 90 00 71 44 90 00 10 Q foo 830 73 19 90 00 72 48 90 00 11 d 3oo 310 74 47 90 00 74 37 90 00 12 *G IS 720 76 45 90 00 76 44 90 00 13 *M 510 80 30 90 00 80 38 90 00 14 *N yoo 6oo 11.2.0 81 35 90 00 81 28 90 00 15 J 610 82 00 90 00 82 10 90 00 16 *L 7co 710 83 08 90 00 83 16 90 00 17 n 8oo 810 84 20 90 00 84 06 90 00 18 / 01 Oil 04 40 54 32 40 54 19 u + 10 + |o 104 90 00 16 28 90 00 15 08 20 t 102 90 00 27 46 90 00 28 03 21 *H + 10 904 90 00 66 31 90 00 67 07 22 r ;11 1. 0.11 90 00 4 20 90 00 4 59 23 *B 123 31 10 34 13 31 47 34 12 24 *E +AtV 5.9.14 34 25 33 48 34 31 34 03 25 (calculated 83° 16'). 14 5 5 Fair . Narrow Broad .do.. 83 19 83 11 82 55 Poor Fair The occurrence of Z{710} on crystal 14 has already been noted under A'{ 11.2.0}. On crystal 5 it is present twice as broad faces, in each case unaccompanied by other rare prisms and forming the only face between a(lOO) and Z(210). Measurements of *H {904}. Crystal Reflection. Size of face. (calculated 67° 07'). 13 14 24 15 16 19 28 31 26 34 20 27 Poor Line face do do 67 06 67 13 67 38 o66 o67 a 66 a 69 68 (^) ("> («-) (b) do........ do No reflection . . do do ...do do do do do do do do do do do a Approximate. b Not measured. This new dome, always present as a hne face, was noted on 12 crystals, as shown in the table. The reflections from the faces were either very poor or not discernible, so that the approximate measure- ments (expressed only in degrees) were made by using the position of maximum illumination. The form is near to the simpler one {201}, but the measurements show that {904} are the correct symbols. The calculated p angle for the form {201} is 64° 37'. Figures 25, 26, 29, 30, 33, and 34 show the new form H{904}. Measurements o/ *5 {123}. Crystal Reflection. Size of face. (calculated 31° 47'). (calculated 34° 12'). 13 19 Poor Small 31 22 30 58 / 34 21 34 05 do Line face On crystal 13 the small face of B gave a poor but distinct reflection. The occurrence is illustrated in figure 25 (p. 66), an ideal representa- NEW FORMS. 61 tion of the crystal, wliich shows two faces of the form. The second side of the crystal is, however, not present, as a cleavage face of (OTO) terminatos that side of the crystal. On crystal 19 the form 5(123} is represented by a line face lying between £'{5.9.14} and /{Oil}, both of which are larger than B, This occurrence is represented in figm'e 29 (p. 67). Tlie form is probably also present on crystal 20, where a nonmeasurable Hne face was observed between J{112} and /{Oil}, though it could not be determined whether the form was {123} or {5.9.14}. Measurements of *E{5. 9. 14). Cgs« Reflection. Size of face. (calculated 34° 31'). (calculated 34° 03'). 19 20 27 Poor Small e / 34 21 34 20 34 35 o / 33 50 34 02 33 31 do do do Line face The first two occurrences of £"{5.9.14} are small faces, much wider than the usual line faces and, as shown in figure 29 (p. 67), the face on crystal 19 reaches a fair size, whereas the corresponding simpler form B{12S} is present as a line face. On crystal 20 (fig. 30, p. 68) the small face of £{5.9.14} lies between J{112} and /{Oil} and also attains an appreciable size. On crystal 27, however, it is present as a mere line face. The symbols for the form E are rather complex and unusual, but the identification of the form on three crystals, the small distinct faces, and the close agreement between measured and calculated angles show that the form is well established. Measurements of *A { 337 } . Cr^U. Reflection. Size of face. (calculated 50° 58'). (calculated 30° 31'). 13 15 20 21 Poor Line face .do 50 47 51 00 51 00 50 13 / 31 08 30 12 30 05 31 03 do do do do do The form A is characteristically a line face between c{001} and J{112}. The only forms in this zone observed on these crystals are m{110}, 6;{111}, J{112}, ^{337}, c{001}, e{112}, and o{Tll}. The form is shown in figiu-es 25 and 30 (pp. 66, 68). *Z>{313}. Only one face of this new form was observed, this being on crystal 19, where a small face yielded a fair reflection whose measurement gave <^, 74° 21' (calculated 74° 44'); p, 47° 21' (calculated 47° 38'). The form is shown in figure 29 (p. 67), 52 COLORADO FEKBERITE AND THE WOLFRAMITE SERIES. FORMS PREVIOUSLY DESCRIBED. COMMON FORMS. The common forms merit only a brief description, as their relative development and occurrence can well be seen by studying the draw- ings illustrating the different combinations and habits. In the prism zone the orthopinacoid a{100} is always strongly striated vertically. These striations are not shown in the crystal drawings. The orthopinacoid is often replaced by vicinal forms sev- eral degrees from the true position of a{100}. On other crystals the faces of a {100} are very close to their true position of 90° 00'. No connection could be traced between the presence of vicinal forms replacing a{100} and the presence of new or rare prisms, as the following table shows : Measurements of a {100} and list of associated prisms. Crystal ^ Remarks. 1 o f90 \90 06 55 }{120>,{940}, {520}, ■{510> present. 3 86 00 No new or rare prisms present. 4 86 57 Do. 5 07 •{810>, {710} present. {710} present. 47 7 f87 188 02 35 |No new or rare prisms present. 8 87 38 Do. 10 {^ 06 11 } Do. 13 89 53 {810}, {510} present. {720}, {510}, {11.2.0}, {810}, {710} present. {810}, {520} present. {810}, { 15.7.0}, {830} present. {810} only rare prism present. 14 90 49 22 23 86 88 49 15 32 89 30 34 r88 \88 24 22 >No new or rare prisms present. 35 i86 26 45 } Do. The common prisms Z{210} and m{110} are striated on some crystals and free from any striae on others, those without striae yielding good and distinct reflections. The base c{001} is generally rounded in the zone {001}: {100}, commonly giving several reflections, the extreme ones on some crys- tals being several degrees apart. The faces of /{Oil}, generally small, all gave good and distinct signals; those of ^{102} were generally distinct, although on a few crystals they were somewhat blurred. The pyramids are generally so small that the reflections from their faces are faint. The striations on J {112} cause the large faces of this form to yield indistinct and blurred signals. The striations are shown in figure 28 (p. 67). FORMS PREVIOUSLY DESCRIBED. 53 RARE FORMS. A number of rare forms which were observed on these crystals are entitled to a short discussion. The results are also applied to the tabulation of the forms of the wolframite group as developed on a later page. r{120}, already noted by Descloizeaux and Jeremejew/ is probably present as a line face on crystal 1; ^ measured 33° 49' (calculated 31° 12'). Q{830}, found by Penfield on hubnerite from Colorado,^ is verified by the presence of two line faces on the crystals herein described. On crystal 18 a line face yielded a fair reflection whose measurement gave (j) a value of 73° 06' (calculated 72° 48'); crystal 23 showed a very narrow face, the measurement of whose reflection gave <^ a value of 73° 32' (calculated 72° 48'). Penfield's^ letter q was changed ^ to Q, as q had already been preempted by the form {103}. d{3l0}, noted by Krenner, Boggild, and as doubtfully present by Moses, was found once on crystal 9 as a very narrow face, giving a poor reflection. <^ measured 74° 47' (calculated 74° 37'). The occurrence is illustrated in figure 24 (p. 66). 7 {6 10} was first described by Boggild, who assigned to the new form the letter p. As this letter had been used by Moses to desig- nate the form {214}, I have changed Boggild's p to j, as here given. The form was noted once, on crystal 9, as a medium-sized striated face; ^ measured about 82° (calculated 82° 10'). The form is shown in figure 27 (p. 67). 71 {8 10}, first noted by Groth and Arzruni, has been observed a number of times on these crystals. Some occurrences are shown in figures 22, 25, and 27. The angles measured are as follows: Measurements o/ n { 810 } . C^SU. Reflection. Size of face. (calculated 84" 06'). 14 17 32 Fair 84 13 83 50 84 23 84 52 84 20 do do do .do. . . Narrow and striated Narrow . do Narrow and striated '^{104}, observed only by Jeremejew, is confirmed by finding it on crystal 13 as a Mne face with t(l02) and 77(904), as shown in figure 25 (p. 66). The reflection was very poor and its measurement gave p 16° 28' (calculated 15° 08'). » See Bibliography, pp. 74-75, for references. * Dana's System of mineralogy, 6th ed., p. 982. « Goldschmidt's Winkeltabellen, p. 366, 1897. 54 COLOKADO FERBERITE AND THE WOLFRAMITE SERIES. /•{1. 0.11}, the only negative dome observed on any of these crystals, was first noted by Groth and Arzruni and is verified by finding it on three of these crystals. The reflections were, however, very poor, owing to the rounded and striated character of the faces. For com- parison the original measurement of Groth and Arzruni is added to the table below. The p angle, as here given, is equal to (001 aT.0.11) — (90°-/3)[ = 0° 28']. The calculated values of p for {T.0.10} and {1.0.12} are also added, and though my own measurements would agree better with these two forms, it is preferable, on account of the poor quality of the reflections, to assign them to the known form HT.O.U}. Measurements of y [1.0. 11). Crystal Reflection. Size of face. p (calculated 4° 59'). 6 9 35 Poor. . Line face do do 3 51 5 23 3 46 do do As measured by Groth and Arzruni, p=4° 59J'. p calculated for <1.0.10>=5'' 32'. p calculated for {1.0.12>=4° 32'. The form r{T.OAl) is illustrated in figures 23 and 24 (p. 66). 2) {2 14} was first described by Moses on a crystal from Boulder Coimty, Colo. It was also noticed by me as narrow faces on crystals 19, 29, and 30 (see figs. 19 and 29, pp. 64, 67), l}dng in the zone c(OOl) : Z(210). The faces gave poor reflections. The angles measured by Moses are also shown in the table below. The form was measured on crystal 19 with the following result: Measurements of p{ 214 } . Angle. Calculated. Measured. Schaller. Moses. ^ p 67 53 29 55 69 42 31 22 68 46 30 17 In addition to the measurements of 2>{214} given above, the form was identified on crystals 29 and 30. These crystals, however, were so incompletely developed that they could not be well placed in polar position. The angle between p(214) and Z(210) was therefore measured, with the following results: Measurements of angle p(214): Z(210). Crystal 29 58 39 Crystal 30 60 05 Calculated 60 05 DISCUSSION OP THE PRISM ZONE. 55 On all three of these crystals the form occurred in the zone c(OOl) : Z(210), and on crystal 19 it was also determined to lie in the zone of and between ^(102) and J (112), so that its determination as (214) is verified by its zonal relations. DISCUSSION OF THE PRISM ZONE. The prism zone contains numerous forms of somewhat complex symbols and a discussion * of these forms is here given in order to show how closely the forms approach the normal series. The entire prism zone from &(010) to a(lOO) shows, when plotted in gnomonic projection (see fig. 35, p. 70), a partition into three parts, the points of division being m(llO) and d(S10). The three zone segments are then: (1) 6(010), r(120), S{7.11.0), m(llO). (2) 7n(110), /(210), i2(15.7.0), C(940), jF'(520), Q(830), rf(310). (3) d(310), (?(720), if(510), N{11.2.0), ;(610), L(710), n(810), a(.100). In the following discussion, these three segments are taken up in turn: (1) Zone segment b m. J. { h r S m ^'^^ lOlO 120 7.11.0 110 Symbol=^ ^2 ll ^ V 7 N^ 7 In place of r or (7.11.0), the simple form 2 or (230) should occur. The form /S (7. 11.0) was not observed by me but was described by Warren. The measured angle (7.11.0) : (7.11.0) is given as 74° 51', whereas the calciilated angle (230) : (230) is 77° 50', a difference too great to allow of the form being referred to the symbol (230). Com- pare also the remarks on page 69 on the indices of this form. Form. (2) Zone segment m d. ( m "\U0 I R C F Q d 210 15.7.0 940 520 830 310 h 1 9 15 ? 5 8 Symbol=^ i J 7 4 2 3 -1. 8 5 3 5 7 4 2 3 -JL 1 1 § 2-v 3 3 i-l. 1 2 3 3 1 12,3 3 2 3 2 > For a description of the methods of the discussion, see Hillebrand, W. F., and Schaller, W, T., The mercury minerals from Terlingua, Tex.: U. S. Geol, Survey Bull. 405, p. 13, 1909. 56 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. The forms fit well into the normal series notwithstanding their complex indices. (3) Zone segment d a. Fonn I ^ ^ ^^ ^~ J L n a 1310 720 510 1L2.0 610- 710 810 100 Symbol=| 3^5 y 6 7 8 oo 1 5 ^^-3 2 ^ 2 34500 v-2 2 1 2 3 00 AT /v 1 1 2 T 3 ^3 - 3 2 3^22 All the new prisms fit well into the normal series. HABIT. _^. J'ive very distinct habits were observed on the crystals examined, babit meanmg the relative development and size of the different crystal faces and the consequent resultant shape of the crystal as a whole. Thus twin crystals are not considered as necessarily of different habit from a simple untwinned crystal. These G^re habits are as follows: 1. Long, narrow, wedge-shaped. This is the habit most frequently observed for the ferberite crystals studied. This is the habit of the penetration twins (figs. 17 and 18, p. 64) but not of the contact twins. (See Pis. VII and VIII, A, pp. 18, 19, and fig. 3.) 2. Short, prismatic, somewhat flattened parallel to the ortho- pmacoid a {100}. Crystals of this habit are fairly abundant. (See Pis. IX, p. 20, and X, p. 21, and fig. 4.) _3. Tabular, parallel to a{100}. Rarely observed in simple crystals but the common habit for the individuals of a contact twin. (See fig. 5, also the twin crystals shown in figs. 14 and 15, p. 63.) . 4. Cubic...j :are. (See PI. VIII, B, p. 19, and fig. C.) 5^ Rhombic, fairly abundant. (See Pis. XI, p. 22, and XII, p. 23, and fig. 7.) Besides the habits mentioned above, two forms were noted which owe their shape to the cleavage of the crystals and are therefore not habits of the mineral. The first of these forms occurs in thin plates, which, as can be seen by reference to figure 8, A (p. 58), owe their tabular appearance to the &{010} cleavage. The complete crystal from which this thin plate was cleaved was probably of the fourth or cubic habit. The second form occurs in long, slender rods and like- wise owes its peculiarity of form to cleavage. As illustrated in figure 8, B, it is probably derived from the edge of a crystal of habit 1 (see figs. 3 and 9), where the prism Z{210} extended to the edge of the crystal. HABIT. 67 Habit 1. The wedge-shaped crystals are generally striated in the prism zone with the forms a{100}, Z{210}, and m{110} grading into one another, as shown in figure 9. On many crystals, however, the individual prism faces are sharply separated and commonly yield single X FiGTTRE 3.— Long, narrow, wedge-shaped crystal of habit 1, the most frequently observed habit. Forms: c{001}, «{100>, 7n{nO}. ?{210}. I , 6{010>, a{100>, 77i{110>, Z{210>,/{011>. FiGUEE 5.— Tabular crystal of habit 3. Common habit for contact twins, but rare for single crys- tals. Forms: c{001}, 6{010}, a{100}, 7n{110}, Z{210>. Figure 6.— Cubic crystal of habit 4. Rare. Form.s: c{001>, 6{010>, a{100>, <{102>. Figure 7.— Rhombic crystal of habit 5. Fairly abundant. Forms: b{010}, a{100>, /{ 102>. distinct reflections. Figure 10 (crystal 4) also represents a tj'pical crystal of this habit. On removing these crystals from the matrix, to which they are firmly attached, they usually cleave, and the result- ing loosened crystal piece will consequently be much shorter in the 58 COLORADO FEBBERITE AKD THE WOLFRAMITE SERIES. H direction of the h axis than the original crystal. From the sharp edge on one side such cleaved pieces show a peculiar axlike shape. (See fig. 11, crystal 2.) The penetration twins (figs. 17, 18, p. 64, and PL VIII, A, p. 19) are generally of this habit, and the contact twins (figs. 14 and 15, p. 63) are of the tabular or third habit. The wedge-shaped crystals of this first habit are generally poor in forms, few being found except the common ones, a{100}, c{001}, Z{210}, m{110}, &{010},/{011}. Habit 2. The short prismatic habit, somewhat flattened parallel to a{100}, is the common habit for the wolframite group in general and is fairly abundant on the Colorado ferberite. An example was shown in figure 4 (crystal 1), and figure 12 illustrates the same combination as shown in figure 4, but with a habit intermediate between the first or wedge shaped and the second or short prismatic . The two habits show all gradations, and it is impossible to refer some crystals to one of these two habits rather than to the other. Fig- ure 12 does not illustrate any partic- ular crystal measured, but many were seen having about the relative pro- portions shown in the figure. Habit 3. The tabular habit may be considered as a further development of the change from habit 1 to habit 2, which is intermediate between habits 1 and 3. Single crystals of this habit, as shown in figure 5, are rare, but in contact twins they are fairly abundant. The orthopina- coid, a{100}-, is strongly striated in the twin crystals of this habit, whereas the other forms in the prism zone are in general nearly free of strise. Habit 4. The cubic crystals were found abundantly on one specimen, aside of which was literally covered with them (PI. VIII, B, p. 19, and fig. 6). They were small, few being over a millimeter in length, and were highly iridescent. Some of the crystals are slightly elongated in the ver- tical direction, whereas others are nearly perfectly cubic. The shape of the crystals is conditioned by the combination being essentially that of the three pinacoids, a{100}, &{010}, c{001}, two of which are at right angles to each other, and the third very nearly so, the angle being 89° 32'. The dome ^{102} is always present, and the pyramid i { 1 12 } is usually developed. The crystals of this habit are very poor in forms. B Figure 8.— Cleavage pieces of crystals. A, thin tabular; B, long, prismatic. Forms: c{001>, 6{010} cleavage, a{100>, 1{210}. HABIT. 59 FiouEK 9.— Striations on wedge-shaped crystals of habit 1, causing a rounded appearance in the prism zone. The top base is also slightly striated and in some crystals rounded. FiQUKti 10.— Crystal 4, wedge-shaped habit, which has sharp, distinct faces, not rounded as in figure 9. Forms: c{001>, 6{010>, c{100>, 7n{110>, i{210>,/{011>. Figure 11.— Peculiar shape of crystals of wedge-shaped habit caused by cleavage on 6{010}. Crystal No. 2. Forms: c<001>, 6{010>, m{no}, /{210>,/{011}. Figure 12.— Crystal of a short prismatic, somewhat Figure 13.— Crystal of rhombic habit, nearly equi- flattened habit. Forms: c{C01>, fe{010>, a{lOO}, wi{110>, Z{210>,/{011>. dimensional. Compare with figure 7, p. 57. Crystal No. 24. Forms: &{010>, o<100>, t{ 102>. 60 COLOEADO FERBEMTE AND THE WOLFRAMITE SERIES. Habit 5. The rhombic crystals are very abundant on some specimens and other habits are then entirely absent. (See Pis. XI and XII.) The rhomboids consist of either a single crystal bounded by plane sur- faces or of an agglomeration of innumerable crystals, each deviating a little more from strict parallelism with the first unit. The crystals are generally elongated parallel to the c axis, as shown in figure 7, though some of them are more nearly equidimensional, as shown in figure 13 (crystal No. 24). The characteristic combination is 6{010}, a{100}, ^{102}, and other forms are rare. Many of these rhombic crystals are fairly large, the longer diameter of .^{102} in average individuals meas- uring nearly half a centimeter. COMBINATIONS. The combinations observed on the 38 crystals measured are shown in the following tables, wherein the different crystals have been grouped according to their habit, as the various habits have a mark- edly different combination. Thus the essential forms, that is, those which are characteristic for a certain habit, are given below for the five different habits observed. The forms are further grouped as promi- nent or not prominent, depending on whether or not they have a decided influence on the shape of the crystal. Forms that are not prominent are placed in parentheses. Characteristic forms for each crystal habit. Form. ^s^er 2. Short pris- matic. 3. Tabu- lar. 4. Cubic. 5. Rhom- bic. c<001 iKOlO a<100 m\m 1{210 mn dm a»{lll ^ c (&) a , m I f c 6 a (m) (/) (0 a (771) c 6 a f: . b a k [::::::::;:; >. (I) (t) t t . ... U) U) ::.:::::::: Combinations on crystals with wedge-shaped habit Form. Crystal No. ■ 2 4 8 29 30 31 32 33 34 35 c{001 \ c b a m I c 6 a m I c b a m I c 6 a m I c b a m I c b a m I R C c b a m I c b a m I c 6 a w, I c 6 a m I WOIO aUOO mhlO H210 i2<15.7 [. |. [ .b> C{940 l^. 1 7l{810 } 1 n f MOll / f f f 'h f "'r"\ H|904 H rh.O. 6><111 liv ^.! to (0 0) 0) CD p|214 |. V V o|lll \. J A \. ' 1 COMBINATIONS. Combinations on crystals with short prismatic habit. 61 Form. Crystal No. 1 3 5 6 7 13 14 15 16 17 18 19 20 21 22 c<001 c b a m I r c h a m I r e b a m I r c b a m I T c b a m I r c b a m I r c b a TO / r c b a TO I c b a TO I c b a TO c b a TO I c 6 a TO I c b a TO c b a TO I e h ! woio 100 m 110> TO 1 rh I 1 { /{210> rh20 i?{15.7.0> R C C 940V C F i F 520> p Q{830 Q a{310> d 720> G M N Jlf{510 M M ■ JV{11.2.0> 1 .... .... N J j/610> ^ 1 L/710V :::j :; • L n n|810> ...^. ........ n / u t H n f /loiiy f f / / f f .... .... / f / / ti{104i t 102> t t H t H t H t t t H t H t t H 904 Jl.o.iii r r ' B 123> B B E ill A £}5.9.14> E 0) A A E "a A at A ^J\\\ (0 a J A "a' w J A w A A 112 > A A A 337> p 214> .. . I B 313i «. 121 s e- Tl2> e 0. In 1 Combinations on crystals with tabular habit. Form. Crystal No. 10 11 12 23 27 28 c{001> c b a TO I c 6 a TO c b a TO R Q n c a c 6 a WOIO} a\ lOOV . . 7n-|ll0> l 210> R{\b 7 0> Q 830V tJsioV / 011/ f / t 102> < H E t H R 904 . . . E. 5.9.14> Combinations on crystals with cubic and rhombic habits. Cubic habit. Rhombic habit. Foim. Crystal No. Crystal No. 38 37 38 24 25 26 c{001, WOIO^ ahoo i{210 «102 fl{904 A{112 c b a c 6 a c b a ...... H f b a I t H 6 a I t H [■• t t A A 62 COLORADO FEKBEEITE AND THE WOLFRAMITE SERIES. TWINNING. Twin crystals were often observed. Only one twinning law was noticed, namely, with {023} as the twinning plane. The many groupings parallel to a{100} were carefully examined for evidences of twinning on the a(lOO) face, but none were seen. As these parallel groupings generally have the i (102) face well developed, twinning on the a (100) face would cause a twinned face of ^(102) to assume the position of (T02), and there would then be an apparent rear orthodome as well as a front one on such a twinned crystal. The absence of such a rear orthodome would indicate that these parallel groupings were not twinned. Though only one twinning law was observed, namely {023}, there were two kinds of twins according to this law, namely, contact and penetration twins. Both were observed many times, though the contact twins are more abundant. The contact twins are illustrated in figures 14 and 15, which show the twinned crystal facing in two directions, or in other words show the two positions a twinned group will take according to which face of {023} acts as twinning plane. Both positions of the twinned group have the same crystallographic relationship. The position shown in figure 14 shows the cHnopinacoid h{010] of the twinned crystal adjoin- ing the same form of the untwinned crystal. In figure 15 the basal pinacoid c{001} of the twinned crystal is shown. In the two illustra- tions the relationships of the contact twins are more clearly indicated than can be done by a written description. The fine of contact of the two crystals affords some points of interest, but for the present only a description of it is given. Theoretically it should be a straight line, as drawn in figures 14 and 15, but actually it is very uneven, the two parts of the twinned crystal being very irregularly dovetailed, as illustrated diagrammaticaUy in figure 16, which was drawn from a twinned crystal (notebook No. A 13), as seen on the goniometer. In the penetration twins tne containing unit is always much larger than the one which is partly embedded and projects out of the middle of the larger crystal, as shown in figure 17. The two crystals, though of different appearance, have the same combination of crystal forms as those shown in figures 14 and 15. Similarly figure 18 shows the same kind of penetration twin with the smaller twinned crystal in the opposite direction to that in figure 17. The large untwinned crystal in figure 18 is shown with one end cleaved off, due to the clino- pinacoidal cleavage &(010). (See PL VIII, A, p. 19.) The angle c{001) : h(010) (fig. 17) is 29° 58', and the angle c(OOl): c(OOl) (%. 18) is 60° 02'. These angular values are here given as reference will be made to them later and the position of the faces forming the angles can here well be seen. TWINNING. 63 A peculiarity notod by Mr. Hess on several crystals similar to the one shown in figure 18 is that in front of the twinned crystal, on the larger untwinned unit, is a small cavity bounded by rough planes which Figure 14.— Contact twin on (053). Forms: &{010>» o{100>,7n{110>,Z{210}. Figure 15,— Contact twin on (023). Forms: c{001}, 6{010>, a{100>, to{110>, ^{210}. Figure 16.— Line of contact of two contact twins. however suggest that they may be slightly developed terminal faces, such as /{Oil}. (See PI. VIII, A, p. 19, center.) They may be caused, however, by crystals of scheelite, jiow removed. 64 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. Figure 17.— Penetration twin on (023). Forms: c{001}, 6{010>, a{100>, m{110}, Z{210>. Figure 18.— Penetration twin on (023). Forms: c<001>, &{010>, o{100>, m{110>, Z{210}. .^ ^' ^f Figure 19.— Crystal 29, showing rare form p. Figure 20.— Crystal 32. Forms: c{001 >, 6{010}, Forms: c{001>,6{010},o{100>,Z{210},p{214}. a{100>, m{110}, ^{210}, A011>,^{112>. Figure 21.— Crystal 33. Wedge-shaped crystal with unequal development of the faces of /. Forms: c{001>, 6{010}, o{100>, m<110>, Z{210},/{011>, J<112>, c^{lll}. COLORADO FERBERITE AND THE WOLFRAMITE SERIES. 66 DESCRIPTION OF MEASURED CRYSTALS. Only such crystals as arc illustrated by drawings will be hero mentioned. The general types of habit have already been shown under the section entitled ''Habit/' where drawings of a few of the measured crystals were also introduced. In general the following figures show the crystals in their ideal development. As most of them were bounded on one side by the cleavage face (OTO) the exact dimension of the crystals in this direction coidd only be estimated, but by observing similar crystals that were intact it is believed that the proportions shown in the figures closely approximate the true relative dimensions. The crystals illustrated will bo grouped under the five habits. Crystal 29 (fig. 19) is simple in its combination but shows the rare form 2^(214} fairly weU developed. It is, moreover, except c{001}, the only terminal form on this crystal. Crystal No. 32 (fig. 20) shows a common combination for a number of minute stout crystals in which the wedge shape is not so characteristic as in crystal No. 33 (fig. 21). Here also the upper and lower faces of /{Oil} arc unequally developed. With the large development of Z{210} the pyramid faces generally become smaller. Crystal 5 (fig. 22) is remarkable in possessing such a small ortho- pinacoid, a{100}, the large faces of n{810} seeming to replace the usually large faces of a. Crystals 6 (fig. 23) and 9 (fig. 24) are both shown in their actual condition, with one side bounded by the cleavage face (OTO). Both of them show a line face of the rare negative dome /-{T.O.I 1} and figure 24 also shows the large positive dome t{102}. The rare prism (^{310} is shown as a line face, and a face of 7 {610}, though not shown, is also present. Crystal 13 (fig. 25) shows a nimiber of new and rare forms, all as narrow faces, generally mere line faces, except one form which is present as a minute equidimensional face. The new forms 7/{904}, J. {337}, J5{123}, and the rare forms n{8l0} and u{104} are the ones referr^ to. The clinodome, /{Oil}, is much narrower and longer than is usual for the faces of tliis form. Crystal 16 (fig. 26) gives a combination seen on numerous crystals not measured. The new form //{904} is generally present on such crystals. Crystal 17 (fig. 27) shows y*{610}, 7i{810}, and o{Tll} besides the more common forms. Crystal 18 (fig. 28) shows the striations observed on i{112}, these strise being parallel to the intersection edges (112) : (001) and (112) : (210), respectively. The crystal is also more elongated in a vertical direction than is usual. Crystal 19 (fig. 29) shows a number of new pyramids, namely, i>{313}, ^{123}, £"(5.9.14}, and the rare pyramid p{214}. The zonal relationships of J (112), £(5.9.14), jB(123), /(Oil), and m'(TlO) could be well seen on this crystal. Crystal 20 (fig. 30) also shows the new form £{5.9.14}, as well as ^{337} and /7{904}. 35659°~Bull. 583—14 5 66 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. -=^=P^^ Figure 22. — Crystal 5, remarkable for its small Figure 23.— Crystal G, with rare form y. Forms: orthopinacoid c{100}. Forms: c{100}, 6<010}, c{001>, fc{010>, g{100}, m-{110>, Z<210}, /{Oil}, c{l(X)}, to{110>, i{210>, n{ 810}, /{Oil}. r{1.0.11}, u){\\\^. 4 I FioUBE 24.— Crystal 9, with rare forms r and d. Forms: c{001}, 6{010}, o{100}, to{110>, Z{210}, d{310}, /{Oil}, t{\Q2}, r{T.0.11}. The form ;{610}, not shown in the figure, is also present on this crystal. Figure 25.— Crystal 13, showing the new forms A,B, and 77 and the rare forms n and u. Forms: c{00l}, &{010}, o{100}, 7n{110}, ^{210}, n{ 810}, /{Oil}, «{104}, t\\Q2}, ir{g04}, ^{337}, ^{112}, w{lll}, .B{123}. MEASURED CRYSTALS. 67 Crystal 36 (fig. 31) shows a cubic crystal somewhat elongated in the vertical direction. The form /{102} is invariably present on these crystals, as is also generally i{112}. Figure 32 illustrates a 4- '& FiQUKE 26.— Crystal 16, a combination observed on FiGxmE 27.— Crystal 17, showing rare forms many crystals not measured. Forms: c{001},6{010>, n, j, and o. Forms: c{001}, 6{010>, a{100>, a-llOO}, to{110}, /{210>, K102>, .ff<904>, J<112>, 6/{lll}. 7n{110}, Z{210}, i{610}, 7Z<810}, <{102>, J{112>, o{Ill}. b Figure 28.— Crystal 18, show- ing striations on A. Forms: c{001>, 6{010}, a{100>, nz{110>, /<210},t{102>,J{112>. FioxJBE 29. — Crystal 19, showing new forms D, B, and E. The zone J{112}, £{5.9.14>, i?{123>, /{Oil}, and m'{110> is well shown. Other forms are c{001}, 6{010>, a{100}, m{\\^}, Z{210>, t<102>, -^{904}, iu{ 111), p<214}, i><313}. cubic crystal apparently slightly elongated in the direction of the a axis, but in reality the original crystal was elongated parallel to the & axis, as the crystal shown in the drawing is incomplete, part of 68 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. FiQUBB 30.— Crystal 20, with new forms //, A, and E. Forms: c{001}, 6{010>, o{100}, m{nQ}, f{210>, /{011>,^{102>, //{904},^{337},J{112>,^111}, E{5.9.U}. c ^^ .^^ t h 1 -^ 1* a } 1 ^ Figure 31. — Crystal 36, a cubic crystal, some- what elongated parallel to its vertical axis. Forms: c{001>, 6{010>, a{100>, f{102>, J{112>. Figure 32.— Cubic crystal (No. 37), apparently elongated parallel to a axis, but in reality elongated parallel to & axis, the left-hand side of the crystal having cleaved off. Figure 33.— Rhombic crystal (No. 25), with the broad orthopinacoid replaced by numerous nar- row alternating feces of a{ 100} and /{ 210). Figure 34. — Crystal 26, a rhombic crystal. Forma: c{001>, 6{010>, a{100>, t{102>, .H{904>. FORM SYSTEM OP THE WOLFRAMITE GROUP. 69 it having cleaved off. The face of <{ 102} is much narrower than that on figure 31. Crystal 25 (fig. 33) shows a rhombic crystal similar to those shown in figures 7 and 13 (pp. 57, 59), with the broad orthopinacoid a{100}, replaced by numerous narrow alternating faces of o{100} and Z{210}, those of Z{210} being much narrower than those of a{100}. The form //{904} is also present. The drawing is, however, but a poor representation of the true appearance of the crystal. Crystal No. 26 (fig. 34) shows the rhombic combination, a, h, t, modified by c{001} and /7{ 904}. FORM SYSTEM OF THE WOLFRAMITE GROUP. CRITICAL STUDY OF FORMS. Before the monoclinic character of wolframite was determined it was considered as orthorhombic, and it is therefore not possible to tell which are the negative and which are the positive forms in the earlier descriptions. The list of forms is fairly extensive, a total of 49 being recorded. Some of these forms will be briefly commented on, as follows: iS'{ 7.11.0} was described by Warren as new and the letter i assigned to it. As, however, i had already been preempted by the form {403}, the letter /S' is assigned to the form {7.11.0}. The measured angle is given as follows: (7.11.0): (7.11.0) =74° 51'. The calcu- lated value is 75° 16' and the calculated value for the simpler form {580} is 74° 16'. The differences between the angles measured and the values calculated are, for {7.11.0} 0° 25' and for {580} 0° 35'. Although the difference is shghtly less for the more complex symbol, the agreement is far from satisfactory. The correct symbol of the form is therefore in doubt, and, though the indices would seem to be possibly simpler than {7.11.0}, these indices are inserted in the table of forms, but are marked with a (?) to indicate that the sym- bols need verification. (See also p. 55.) w{021} was noted only by Descloizeaux and by Jeremejew. Attention is called to the fact that {021} occupies almost exactly the same position as c{001} in twin position. It is therefore possible that a face of c{001} in twin position (as shown in fig. 35) was measured and taken for (021). c(OOl) : m;(021)=60° OV (calculated). c(OOl) : e(001)=60° 02' (calculated; p. 62 The difference between the two values is so small as to be unmeasur- able. It seems right, therefore, to regard the form w{02l) as doubt- ful and as at least needing verification before it can be accepted as a definite form. 70 COLORADO FERBEKITE AND THE WOLFRAMITE SERIES. ^{095}, found only by Descloizeaux, also needs verification. The measured angle agrees much better with the slightly more complex form {0.11.6}. (Oil) : (095) =16° 47^ (measured by Descloizeaux). (Oil) : (095) =16° 26^ (calculated); difference =+2K (Oil) : (0.11.6)=16° 64' (calculated); difference =-07^ The form is therefore considered doubtful, on account of the im- certainty of its symbol and because it needs verification. \ www 1 III 1111/ /' \ 4 k i / / / h b - £ \r , V / r.^' \ /^' J^ \ ^vN r^.> w^^ / Tv^X \ .^ -^ R^ ^/ ^7V &> \ y ''"/ H \ ^ \ \ 1 ^ K / / ////// i . mm. \ \ Figure 35. — Gnomonic projection of forms of the wolframite group. Several forms are plotted in twin X)osition (open circle) to show their close position to untwinned forms. Thus note particularly c and w, i and t, i[ and a, t and s, s and «, 4 and V. ^{304}, described only by Groth and Arzruni, is also doubtful, as the measured angles vary considerably from the values calculated for them. Angles for the form ^{304}. Angle. Measured. Calculated. Difference. (001) :(S04) (102) :(304) (304): (101) 39 56 11 51 9 17 38 23 10 30 8 15 + 1 33 + 1 15 + 1 02 FORM SYSTEM OP THE WOLFRAMITE GROUP. 71 >1{T01}, described first by Groth and Arzruni and later noted by Groth (but without measurement), is also doubtful. (001) : (TOl) — 48° 37' measured and 46° 38' calculated, the difference being 1° 59'. z{113} given by Miller ^ has always been considered a questionable form. Though inserted by Goldschmidt in his Winkeltabellen with a query, it had best be omitted. The symbol may be a misprint for {112}. Eakle gives the letter v to a new form {T22} on wolframite from Nevada, but as the letter v is already preempted by the form {552}, Eakle's letter is changed to V. Eakle's letter li should be changed to d and d changed to e. It may be noted, too, that the correctness of the positive or nega- tive character of several of the forms listed is very questionable. This is particularly true of the domes described by Krenner, who himself called attention to this uncertainty. Figure 35 shows the gnomonic projection of all the known forms of the wolframite series except t{321}, which falls outside of the projec- tion, and x{754}, which was described after the gnomonic projection was drawn and reproduced. The position of the forms is indicated in figure 35 by dots, whereas the position of some of the forms in twin position (twinned on {023}) is shown by open circles. All the forms lie in well-developed zones. The prism zone is the richest, containing a total of 17 forms, but hardly any of the simple zones are poor in forms. The position of many of the twinned forms is nearly identical with other forms which are not twinned and which are in their normal position, as, for example, ^{T02} and g{121}, c{001} and w{02l}, i{102} and s{T21}, .9{T21} and ^{102}, ^{121} and y{T02}, fi{l21} and5{T21}. FORMS AND COORDINATE ANGLES. The following table of forms and coordinate angles shows several points to which attention may be called. If a form is considered doubtful — that is, if it seems uncertain whether such a form actually exists — the question mark used to indicate this is placed with and immediately following the letter of the form. Thus w ?{021 } means that there is doubt as to whether such a form has actually been found. If, on the other hand, there is no question about the existence of the form, but the symbols seem to be incorrectly determined, or at least a verification of the correctness of the measurement is desired, the question m-ark is placed after the symbols, thus /S'{7.11.0} ?. References are given when the form has been seen and described by only one observer or two independent observers. If at least three different observers have noted the form its confirmation would seem 1 Miller, W. H., Elementary introduction to mineralogy, p. 473, 1852. 72 COLORADO FEBBEEITE AND THE WOLFRAMITE SERIES. to be SO well established that references to it are in general not neces- sary. The occurrence of the form on the three members of the wolframite group has also been noted. Forms and coordinate angles, wolframite grou^. [a=0.8255; c-0.8664; /9=89'' 32'.] No. 37 Letter. c b a r 8 m I R C F Q d G M N i n wt gf f r tt ? y t df kf h i H k C V s Symbol. Gold- schmidt. Miller. 001 Ooo 010 oo 100 oo2 120 oo -V- 7.11.0? oo 110 2oo 210 -V- oo 15. 7. ioo 940 |oo 520 IS 830 310 Joo 720 500 510 V03 11.2.0 6oo 610 Too 710 SCO 810 02 021 Of 095 01 Oil -tVO LO.ll + 104 +J0 -io 103 102 + iO 102 -jo 304 -10 101 + 10 101 -JO 403 +1 904 -f 602 132 — i 1 122 -12 121 + 12 121 +H 123 +A T*l 5.9.14 + H 313 -i 112 -1 111 -f S52 + 1 111 + i 112 +f 337 +51 754 -i? i?l +H 214 90 00 00 90 00 31 12 37 38 50 27 67 34 68 58 69 51 71 44 72 48 74 37 76 44 80 38 81 28 82 10 83 16 84 06 16 18 32 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 21 41 30 48 31 00 31 24 31 47 34 31 47 21 50 01 50 14 50 22 50 40 50 53 50 58 59 35 61 14 67 29 67 53 28 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 90 00 60 00 57 20 40 54 4 59 15 08 19 41 27 19 28 03 37 55 46 10 46 36 54 17 67 07 69 04 54 26 45 15 63 41 63 46 34 12 34 03 74 44 33 59 53 34 73 35 53 49 34 29 30 31 64 57 74 29 66 10 29 55 Refer- 12 13 4,13 2,3 2 4,13 3,13 3 Ferberite, FeWOi. 4 4,6 5,6 7 ii'is Wolframite, (Fe,Mn) WO.. Hiibnerite, MnWOi. a Numbers refer to the Bibliography, pp. 74-75. COLORADO FERBERITE AND THE WOLFRAMITE SERIES. 73 COMBINATIONS OBSERVED ON THE WOLFRAMITE GROUP. The following table shows the combinations described on minerals of the wolframite gi-oiip commencing with the definite sstablishmcnt of the monoclinic character of the group by Descloizeaux in 1 850. As wolframite was considered to be orthorhombic in the earlier debcriptions, the combinations of those writers are not given, as the positive and negative forms can not be differentiated. Numbers after names of authors refer to similar numbers in the bibliography. Combination No. 10 gives the entire list of forms mentioned by Descloizeaux and doubtless represents several crystals, in part prob- ably the same as combinations Nos. 1, 2, and 3. Combination 11 hkewise gives the complete list of forms observed by Jeremejew, as I was not able to decipher the individual combinations from the Russian text. CoTnbinations described on crystals of minerals of the woljramite group. No. Combination. bamlfoo) amlfoo) amlfgyt cbamlfyt c o 7n l/s 0(0 amlfyts amlfytso arml/yts bamtot cbarmlwgfytSffOd). cbarmlwfuqytSffOt cbamriTryirXtot bak ; baik badik cbd bat bayh bay bhv baiv cbadyik^e cafho amlXhffo) bam cbamlfyaoeoazi amfy b(ajmdftcj b(a)mQt b(a)mQtJ amlft amfo cbaSmlfytJ camlfytsirOeo. cb{a)mltj p... cbamdj/yteooiJ. cbaml/tow cbarmadstoe V. cbamlatx Mineral. Wolframite. do do do .do. .do. .do. .do. .do. .do. .do. ....do.. ....do.. ....do.. Iliibnerite., Wolframite. do Hubnerite.. ....do do Wolframite. do Ferberite... Wolframite. Ferberite... ....do Wolframite. do.o... HUbnerite. . Locality. Chanteloube. do do Altenberg do Zinnwald do do Schlaggenwald . Chanteloube... Altai, Russia... Schlaggenwald. Felsobanya. do .do. ....do. ....do. ....do. do.... Altenberg. Zinnwald. Spain Fiehtelgebirge Silverton,Colo... New Mexico , do Altai Japan South Dakota (Colorado?). New South Wales. Boulder County, Colo. Greenland Bolivia Nevada Peru Author. Descloizeaax (1). ...-do.(l) -..-do.(l) .do.(l). .do.(l). .do.(I), .do.(l). do.(l) do. (2) do. (2) Jeremejew (3) Groth and Arz- runi (4). Krenner (5) , do.(5) do.(5) do.(5) do.(5) do.(5) , do.(5) do.(5) do.(5) do.(5) Groth(6) do.(6) Bertrand (7) Seligman(8) Sandbergcr (9) Penfleld(lO) do. (10) do.(lO) Jeremejew ( 11 )... . Jimbo(12) Warren (13) Anderson (14). Moses (15) B6ggild(l«)... Spencrer(17)..- Eakle(18) Tronquoy(19)- Date. 1850 1850 1850 1850 1£50 1850 1850 1850 1870 1870 1872 1873 1875 1875 1875 1875 1875 1875 1875 1875 1875 1875 1878 1878 1882 1880 1888 1892 1892 1892 1901 1904 1905 1905 1907 1912 1913 o Eaklo states that "All of the material contains iron and is to be classed as wolframite rather than as hubnerite." His next sentence, " The crystals aro tabular parallel to tho orthopinacoid and some of them are exceedingly thin and almost transparent, wiih a deep-red color," would indicate, however, that the material was more likely hubnerite than wolframite. 74 COLORADO FERBERITE AND THE WOLFRAMITE SERIES. The following combinations were observed by the writer on the ferberite from Colorado described in this report: cbamlf cbamlfrioeo chamlf cbamlf cbamlfo cbaml cbamlf (u cbamldjf trwo cbamlf cbamlp cbamlMnfut IIBcuJA cbamlRQnft cbamlp cbamlGMNLntHAso cbatllE cbamlRCHto cbamlftllwJA cbatH cbamlf o) cbamlt IIwJ cbatj cbamlf (upo cbaml Nnftjo cbat cbamlf H(ao cbamlR CQtj cbaltj cbamlfrcao cbamlf t HB Em JpD baUH cbamlr CFMf cbamlftHwJA baltH cbamlf cbamlft EAA cbatH cbamlLnf cbaml Fftwd By calculatiQg the percentage occurrence for the 77 combuiations listed (the 39 given in the table and the 38 observed by the writer), the forms of the wolframite group fall into three classes, as follows : (1) Prominent forms: Letter a h m c I ft Symbol (100) (010) (110) (001) (210) (Oil) (102) Per cent of occurrence 97 84 75 67 67 57 51 (2) Less prominent forms: Letter co o d y H s o Symbol (Ill) (111) (112) (T02) (904) (121) (121) Per cent of occurrence 35 24 21 21 17 12 11 (3) Rare forms: AH the remaining forms, 35 in immber. BIBLIOGRAPHY. 1. Descloizeaux, A., Memoire sur les formes cristallines du wolfram: Annales chim. et phys., 3d ser., vol. 28, p. 163, 1850. 2. Descloizeaux, A., Nouvelles recherches cristallographiques et optiques sur la forme clinorhombique du wolfram: Annales chim. et phys., 4tli ser., vol. 19, p. 168, 1870. 3. Jerfemejew, P., Wolfram- Krystalle im Vergleich zu den Krystallen des Columbite: Russ.-k. mineral. Gesell. St. Petersburg Verb., 2d ser., vol. 7, p. 301, 1872. 4. Groth, P., and Arzruni, A., Ueber die Krystallform und die optische Eigenschaften des Wolframs und dessen Beziehungen zum Columbit: Poggendorff's Annalen, 5th ser., vol. 29, p. 235, 1873. 5. Krenner, J. A., Wolframit aus dem Trachyte von Felso-Banya: Min. pet. Mitt., vol. 5, p. 9, 1875. 6. Groth, P., Die Mineraliensammlung der Kaiser- Wllhelms-Universitat, Strassburg, p. 161, 1878. 7. Bertrand, E., Sur la hubn^rite des Pyr^n^es: Soc. min. de France Bull. 5, p. 90, 1882. 8. Seligmann, G.,MineralogischeNotizen, III; 12, Wolframit: Zeitschr. Kryst.Min., vol. 11, p. 347, 1886. 9. Sandberger, F., Ueber Lithionitgranite mit besonderer Rucksicht auf jene des Fichtelgebirges, Erzgebirges und des nordlichen Bohmens: K. bayer. Acad. Miinchen, Math. -phys. Classe, Sitzungsber., 1888, p. 423. 10. Penfield, S. L. (with Genth, F. A.), Mineral notes, No. 52: Am. Jour. Sci., 3d ser., vol. 43, p. 184, 1892. BIBLIOGRAPHY. 75 11. JeremeJGw, P., Ueber den Wolf rami t von der Demidow'schen Kupfergrube in der Niihe dos Kolywan'schen Bergwerkes, Altai: Russ.-k. mineral. Geaell. Verb., vol. 31, p. 404, 1894. 12. Jimbo, K., Notizen (iber die Mineralien von Japan: Tokyo Coll. Sci. Jour., vol. 11, p. 213, 1899. 13. Warren, C. H., Mineralogical notes: Crystal of iron wolframite from South Dakota: Am. Jour. Sci., 4th sor., vol. 11, p. 372, 1901. 14. Anderson, C, Mineralogical notes No. I: Topaz, beryl, vesuvianite, tourmaline, and wolframite: Australian Mus. Records, vol. 5, p. 303, 1904. 15. Moses, A. J., The crystallization of luzonite and other crystallographic studies; Crystallized wolframite from Boulder County, Colo.: Am. Jour. Sci., 4th ser., vol. 20, p. 281, 1905. 16. Boggild, O. B., Mineralogia Groenlandica: Meddelelser om Greenland, No. 32, p. 179, 1905. 17. Spencer, L. J., Minerals from Bolivia: Mineralog. Mag., vol. 14, p. 334, 1905. 18. Eakle, A. S., The minerals of Tonopah, Nev.: California Univ. Dept. Geology Bull., vol. 7, p. 18, 1912. 19. Tronquoy, R., Surla hubn^rite: Soc. fran?. min^ralogieBull. 36, p. 113, 1913. O