'-? STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES BARITE DEPOSITS NEAR BARSTOW SAN BERNARDINO COUNTY CALIFORNIA SPECIAL REPORT 39 DIVISION OF MINES FERRY BUILDING, SAN FRANCISCO SPECIAL REPORTS ISSUED BY THE DIVISION OF MINES 1-A. Sierra Blanca limestone in Santa Barbara County, Cali- fornia, by George W. Walker. 1950. 5 pp., 1 pi. Price 25*. 1-B. The Calera limestone, San Mateo and Santa Clara Counties, California, by George W. Walker. 1950. 8 pp., 1 pi., 6 figs. Price 25 *. 2. Geology of part of the Delta-Mendota Canal near Tracy, Cali- fornia, by Parry Reiche. 1950. 12 pp., 5 figs. Price 25*. 3. Commercial "black granite" of San Diego County, California, by Richard A. Hoppin and L. A. Norman, Jr. 1950. 19 pp., 18 figs. Price 25*. 4. Geology of the San Dieguito pyrophyllite area, San Diego Countv, California, by Richard H. Jahns and John F. Lance. 1950. 32 pp., 2 pis., 21 figs. Price 50*. 5. Geology of the Jurupa Mountains, San Bernardino and River- side Counties, California, by Edward M. MacKevett. 1951. 14 pp., 1 pi., 14 figs. Price 25*. 6. Geology of Bitterwater Creek area, Kern County, California, by Henry H. Heikkila and George M. MacLeod. 1951. 21 pp., 2pls., 15 figs. Price 35*. 7-A. Gem- and lithium-beariug pegmatites of the Pala district, San Diego County, California, by Richard H. Jahns and Lauren A. Wright. 1951. 72 pp., 13 pis., 35 figs. Price $2.50. 7-B. Economic geology of the Rincon pegmatites, San Diego County, California, by John B. Hanley. 1951. 24 pp., 1 pi., 5 figs. Price 35*. 8. Talc deposits of steatite grade, Inyo County, California, by Ben M. Page. 1951. 35 pp., 11 pis., 25 figs. Price 85*. 9. Type Moreno formation and overlying Eocene strata on the west side of the San Joaquin Valley, Fresno and Merced Counties, California, by Max B. Payne. 1951. 29 pp., 5 pis., 11 figs. Price 60*. 10-A. Nephrite jade and associated rocks of the Cape San Martin region, Monterey County, California, by Richard A. Crippen, Jr. 2d printing. 1951. 14 pp., 14 figs. Price 25*. 10-B. Nephrite in Marin County, California, by Charles W. Chester- man. 1951. 11 pp., 16 figs. Price 25*. 10-C. Jadeite of San Benito County, California, by H. S. Yoder and C. W. Chesterman. 1951. 8 pp., 6 figs. Price 25*. 11. Guide to the geology of Pfei£fer-Big Sur State Park, Monterey County, California, by Gordon B. Oakeshott. 1951. 16 pp., 1 pi., 28 figs. Price 25*. 12. Hydraulic filling in metal mines, by William E. Lightfoot. 1951. 28 pp., 15 figs. Price 50*. 13. Geology of the saline deposits of Bristol Dry Lake, San Ber- nardino County, California, by Hoyt S. Gale. 1951. 24 pp., 1 pi., 2 figs. Price 35*. 14. Geology of the massive sulfide deposits at Iron Mountain, Shasta County, California, by A. R. Kinkel, Jr., and J. P. Albers. 1951. 19 pp., 6 pis., 6 figs. Price 75*. 15. Pbotogeologic interpretation using photogrammetric dip cal- culations, by D. H. Elliott. 1952. 21 pp., 9 figs. Price 50*. 16. Geology of the Shasta King mine, Shasta County, California, by A. R. Kinkel, Jr., and Wayne E. Hall. 1951. 11 pp., 3 pis., 4 figs. Price 50*. 17. Suggestions for exploration at New Almaden quicksilver mine, California, by Edgar H. Bailey. 1952. 4 pp., 1 pi. Price 25*. 18. Geology of the Whittier-La Habra area, Los Angeles County, California, by Charles J. Kundert. 1952. 22 pp., 3 pis., 19 figs. Price 50*. 19. Geology and ceramic properties of the lone formation, Buena Vista area, Amador County, California, by Joseph A. Pask and Mort D. Turner. 1952. 39 pp., 4 pis., 24 figs. Price 75*. 20. Geology of the Superior talc area, Death Valley, California, by Lauren A. Wright. 1952. 22 pp., 1 pi., 15 figs. Price 50*. 21. Geology of Burruel Ridge, northwestern Santa Ana Moun- tains, California, by James F. Richmond. 1952. 1 pi., 11 figs. Price 50*. 22. Geology of Las Trampas Ridge, Berkeley Hills. California, by Cornelius K. Ham. 1952. 26 pp., 2 pis., 20 figs. Price 75*. 23. Exploratory wells drilled outside of oil and gas fields in Cali- fornia to December 31, 1950, by Gordon B. Oakeshott, Lewis T. Braun, Charles W. Jennings, and Ruth Wells. 1952. 77 pp., 1 pi., map. Price, map and report, $1.25 ; map alone, $1. 24. Geologv of the Lebec quadrangle, California, by John C. Crowell. 1952. 23 pp., 2 pis., 10 figs. Price 75*. 25. Rocks and structure of the Quartz Spring area, northern Panamint Range, California, by James F. McAllister. 1952. 38 pp., 3 pis., 13 figs. Price 75*. 26. Geology of the southern Ridge Basin, Los Angeles County, California, by Peter Dehlinger. 1952. 11 pp., 1 pi., 7 figs. Price 50*. 27. Alkali-aggregate reaction in California concrete aggregate* by Richard Merriam. 1953. 10 pp., 12 figs. Price 35*. 28. Geology of the Mammoth mine, Shasta County, California, by A. R. Kinkel, Jr., and Wayne E. Hall. 1952. 15 pp., 9 pis., 5 figs. Price 75*. 29. Geology and ore deposits of the Afterthought mine, Shasta County, California, by John P. Albers. 1953. 18 pp., 6 pis., 9 figs. Price 75*. 30. Geology of the southern part of the Quail quadrangle, Cali- fornia, by Charles W. Jennings. 1953. 18 pp., 2 pis., 16 figs. Price 75*. 31. Geology of the Johnston Grade area, San Bernardino County, California, by Robert Barton Guillou. 1953. 18 pp., 1 pi., 19 figs. Price 75*. 32. Geological investigations of strontium deposits in southern California, by Cordell Durrell. 1953. 48 pp., 9 pis., 12 figs. Price $1.25. 33. Geology of the Griffith Park area, Los Angeles County, Cali- fornia, by George J. Neuerberg. 1953. 29 pp., 1 pi., 15 figs. Price 50*. 34. Geology of the Santa Rosa lead mine, Inyo County, Califor- nia, by Edward M. Mackevett. 1953. 9 pp., 2 pis., 3 figs. Price 50*. 35. Tungsten deposits of Madera, Fresno, and Tulare Counties, California, by Konrad B. Krauskopf. 1953. 83 pp., 4 pis., 52 figs. Price $1.25. 36. Geology of the Palen Mountains gypsum deposit, Riverside County, California, by Richard A. Hoppin. 1954. 25 pp., 1 pi., 32 figs., frontis. Price 75*. 37. Rosamond uranium prospect, Kern County, California, by George W. Walker. 1953. 8 pp., 5 figs. Price 25*. 38. Geology of the Silver Lake talc deposits, San Bernardino County, California, by Lauren A. Wright. 1954. 4 pis., 18 figs. Price $1.00. 39. Barite deposits near Barstow, San Bernardino County, Cali- fornia, by Dordell Durrell. 1954. 8 pp., 4 pis., 1 fijf. Price 50*. STATE OF CALIFORNIA GOODWIN J. KNIGHT. Governor DEPARTMENT OF NATURAL RESOURCES DeWITT NELSON. Director DIVISION OF MINES FERRY BUILDING. SAN FRANCISCO 11 OLAF P. JENKINS. Chief \N FRANCISCO SPECIAL REPORT 39 APRIL 1954 BARITE DEPOSITS NEAR BARSTOW SAN BERNARDINO COUNTY CALIFORNIA By CORDELL DURRELL Geological Survey. U. S. Department of the Interior Price 50^ BARITE DEPOSITS NEAR BARSTOW, SAN BERNARDINO COUNTY, CALIFORNIA* By Cordell, Durrell, *• OUTLINE OF REPORT rocks, a small area of tuff of Tertiary age, and Recent General statement .L^l alluvial deposits (pi. 1). The rocks trend northward; Ball barite deposit 3 from west to east they consist of an unknown thickness Barite deposits in the vicinity of the Barium Queen mine 4 of metamorphosed elastic sedimentary rocks, chert, lime- 3ansen barite deposit and vicinity ____________ 5 st0 ne, silicic tuff and flows; a belt of marble about 200 3ante deposits at the Lead Mountain mine and vicinity 7 j? . -v- i • vt._i.v-_ u i_ e i *- selected references __ ____ _ 8 ee * thick in which the barite occurs ; a belt of slates, quartzites, and silicic tuffs about 130 feet thick; and an illustrations unknown thickness of metamorphosed basic volcanic ™ . -. „ _ -, ■,-, _ ■_ _ •_ c -™ _- „ rocks, dark schists, and interbedded slates. Plate l. Map of Ball barite deposit, San Bernardino Countv, m , , . , . , , , . „ California in pocket * " e roc ^ in which the barite occurs consists of a rami- 2. Map of Barium Queen mine and vicinity, San Ber- f y in _" network of calcite veins and irregular masses of nardino County, California In pocket white marble in gray schistose marble. The white marble 3. Map of Hansen barite deposit, Ludlow, San Ber- probably resulted from recrystallization, either by con- nardino County, California In pocket tact or by hydrothermal metamorphism, of the gray 4. Map of Lead Mountain and vicinity, San Bernardino marble. Veins and pods of tremolite fill cross faults in County, California In pocket the marb l e and are found along the fault near the west figure 1. Index map of barite deposits near Barstow, San edg . e f the belt ( p l. 1). The tremolite probably resulted Bernardino County, California 4 <• „ ■, ,„ , , • from hydrothermal metamorphism. GENERAL statement ^ e roc ^ s ex P°sed east of the marble are dark-colored blastoporphyritic amphibolites, hornblende and chlorite The material in this report was compiled from field schists, and thin beds of slates and light-colored schists, tudies made of barite deposits during the latter part of The dark schists were probably formed by dynamo- JVorld War II. The work was done as a part of the Stra- thermal metamorphism of flows and tuffs that were an- egic Minerals Investigations carried on by the U. S. desitic to basaltic in composition. The thin slates and Jeological Survey. No prior reports on the deposits have light-colored schists are believed to have been formed »een published ; however, all the deposits are briefly re- f rom the metamorphism of interbedded clastic sedimen- erred to in mineral resource reports of the California tary rocks and rhyolitic tuffs. These rocks are continu- )ivision of Mines. ously exposed for a distance of half a mile to the east ; Four localities are described in this report : the Ball farther eastward they are covered by alluvium, .arite deposit, barite veins in the vicinity of the Barium Unmetamorphosed tuff overlies the dark schists near Jueen mine, the Hansen barite deposit, and barite de- the southern edge of the mapped area. The tuff is cream- josits at the Lead Mountain mine and vicinity. These colored, thin-bedded, and fine-grained; rhyolitic; and leposits have been grouped together in one report be- probably Miocene in a°-e ause all are in the vicinity of Barstow, California, and, The rocks in the arel trend northward and generally 7ith the exception of the Hansen deposit, within a few di 50 o to 6Q o E To the east the marble g to Qiles of one another; all are vein deposits; and the pat- be CO nformable with the beds but to the west it is bor- ern of future exploration and mining would be similar dered by a fault The fault trends n0rthward and dips or each deposit. The individual deposits have been at about the same angle as the bedding, but the fact reated separately in this report, as each is unique in t hat the beds beneath the fault are successively cut out tructural stratigraphic, and mmeralogic relationships to t he north indicates discordance. The magnitude of md each has been exploited to a different degree. this fault is not kn0W n. Many cross faults cut the marble The writer wishes to acknowledge the courtesies shown and offset the main north-trending fault, and several of am by the owners of the properties. A. C. Daley ably t hese cross faults terminate against it. It is probable ■ssisted in the field and in the preparation of the illus- t hat all of the faults are of the same relative age; and, rations. as bo t b the main fault and many of the smaller faults BALL barite DEPOSIT contain tremolite, the faulting occurred about the same The Ball barite deposit is about 15 miles northeast of time as the tremolitization, or earlier. Barstow in the SB^ sec. 8, T. 11 N., R. 1 E., San Ber- Barite Veins. The barite occurs in veins in the lardino County, California (fig. 1). It is at the western marble east of the main north-trending fault in a zone :nd of the Calico Mountains and half a mile west of the that is nowhere more than 70 feet wide. The barite is >aved road connecting Barstow and Camp Irwin. The fine-grained and massive. The amount of impurities pres- >roperty consists of two claims, held in 1945 by O. H. ent in the veins is small, and the barite, upon weathering, Sail of Los Angeles. A brief description of the property develops only a faint brown iron stain. The veins are s given by Tucker and Sampson (1943). a fraction of an inch to 2 feet wide. They trend north- n„„i„„ -v. i j • _.i_ '••■___> _i ward and dip 14° to 57° E. Cross faults have cut the ift 7 he r + 0cks ? x + p0S / d l?.?" 5 vlcmit y °/ the veins, brecciating the barite into angular blocks that Bal barite deposit consist of a thick sequence of pre- later ' we re recemented by granular calcite. The age of cetaceous metamorphosed sedimentary and volcanic emplacement of the barite is not known; however" the * Publication authorized by the Director, TJ. S. Geological Survey. emplacement Occurred before the cross faulting and Geologist, U. S. Geological Survey. Manuscript submitted for pub- _ v_- _• lication August, 1953. tremolltization. (3) Special Report 39 Figure 1. Index map of barite deposits near Barstow, San Bernardino County, California. North of the mapped area the marble is partly silici- fied and has been replaced by predominantly brown but also yellow and red chalcedony and microcrystalline quartz. The silicified zone was traced for a mile to the north, where the marble is covered by alluvium. Similar silicified marble was traced for half a mile to the south, the limit of exposure of the beds. Silicified marble is rare near the barite veins, and nowhere has barite been found in association with the silicified rock. The silicification is believed to have occurred during Tertiary time and is probably related to the silver-lead- zinc mineralization of the Calico Mountains and the sur- rounding country. Many of the low-grade Tertiary silver veins in the region to the south contain barite ; however, the barite differs in occurrence and association from that in the veins of the Ball deposit. Workings. The two claims covering the Ball deposit were filed in July, 1941. Subsequently 11 open-cuts and two 10-foot adits were made on the property. It is esti- mated that about 500 tons of barite was obtained from the larger cut in the southern area near the end of the road. The amount of barite quarried from the large cut at the extreme southern end of the workings, although substantial, was probably not as great. None of the other cuts have yielded important amounts of barite. Reserves. As may be seen on the accompanying map (pi. 1), the barite veins are very thin. Near the center of the southern workings a vein 1 foot thick crops out but this thickness is maintained for only about 30 feel! along the strike. The only veins wide enough to warrant attention are those that have been quarried at the big cut near the end of the road in the central part of th< southern workings. Here surface mining is no longeil practicable, and it would be necessary to begin under ground workings. The maximum thickness of the barit( in these veins is 4 feet, but the average thickness foi a length of 70 feet is not more than 2 feet. In additior there is no indication that the veins widen or even con- tinue in depth. The known minable reserve of barite is small in the present state of development of the deposit BARITE DEPOSITS IN THE VICINITY OF THE BARIUM QUEEN MINE The Barium Queen mine is about 5 miles northeasl of Barstow, in San Bernardino County, California (fig. 1), near the east end of a low range of hills. Th< mine is in the NEi sec. 27, T. 10 N., R. 1 W. From i point southeast of the mine the barite-bearing veins ex tend northwestward into sees. 21,. 22, and 28 of the same township. The area is accessible from both the nortl and the south by good ungraded roads. Six claims along the three principal veins were pat ented in 1906 by Charles Mushrush. In 1945 the three western claims were owned by the State of California and the three eastern claims, known from north to soutl as the Barium Queen, the White House, and the White Barite Deposit Near Barstow louse Extension, were owned by Justin Snow of Los uigeles. Brief descriptions of the Barium Queen mine are iven by Bradley (1930, pp. 54-55) and Tucker and lampson (1931, p. 137; 1943, pp. 508-509) in reports f the California Division of Mines. Geology. Biotite-hornblende gneiss is the principal ock in the area. Northwest of the Barium Queen mine, owever, are interbedded layers of fine conglomerate, ebbly quartzite, and a bed of marble 25 feet wide pi. 2). The presence of these metasedimentary rocks in lie gneiss suggests that the gneiss was derived by meta- lorphism of sedimentary rocks. Several small pegmatites nd a granitic dike, too small to be shown on the map, rop out in the area. The age of the rocks is not known. Bedding planes were found only near the marble, but well-developed cleavage was mapped in both the mar- ie and the gneiss. This cleavage is parallel to the bed- ing in the interbedded quartzite and probably reflects tie attitude of the bedding throughout most of the neiss. Dips throughout much of the area are gentle, nd the strike is irregular. Small folds are apparent in lie gneiss, but no large folds were found. Lineation is ronounced on most of the cleavage surfaces. Two sets of joints, one trending N. 30° W. and the ther N. 50° W., cut the gneiss. Along each trend the aint planes dip steeply to both the northeast and the juthwest at angles of 20° to 30° from each other, and s a result the gneiss weathers into elongate rhomb- haped blocks. The trend of the barite veins is similar D that of the joints. Barite Veins. Three main veins, several lesser veins, nd many small branches of these veins contain barite t the Barium Queen mine and vicinity. The main veins -east, middle, and west — follow faults that displace the neiss and the marble. The horizontal displacement along he faults is about 100 feet. The east vein is continuous or 3,400 feet, the middle vein for 6,200 feet, and the rest vein for 4,800 feet. The veins parallel the joints a the gneiss, following first one set and then another, nd thus have many changes of attitude. On the small- cale map (pi. 2) and on the surface, these changes of rend appear angular and abrupt, although in reality lany are curved and gradual, as is shown on the de- ailed map and sections (pi. 2). The veins are composed •rimarily of quartz and barite. In some places the veins onsist entirely of either quartz or barite, and in other ilaces the two minerals are intermixed so that the width f the vein at any particular place does not necessarily eflect the amount of either mineral present. The vein latter is in many places accompanied by fault gouge, >ut little of the barite is brecciated. The process of vein ormation during the stage of the introduction of the iulk of the barite seems to have been essentially the illing of a fissure without accompanying fault move- nents. The age of the barite veins in the immediate 'icinity of the Barium Queen mine is not known, but he veins are similar mineralogically to a system of r eins cutting rocks of probable Miocene age in the Lead /fountain district 2 miles southeast. The middle and the east vein each contains important imounts of barite. Along most of the exposed length of he middle vein the barite is more than a foot thick. West of locality A (pi. 2) a 100-foot segment of the vein contains barite that averages 10 feet in thickness, and a considerable part of the rest of the vein contains barite that is between 3 and 5 feet thick. Six segments in the middle vein range from 400 to 1,000 feet in length and contain barite that averages from 1 to 10 feet in thickness. The east vein is more uniform in thickness, and the barite content can be described more simply. The 1,800-foot segment from the Barium Queen mine to the sharp bend near the north end of the vein con- tains barite that averages 2 feet in thickness. The part of the vein north of the sharp bend on the north side of the ridge and the part southeast of locality A (pi. 2) are too thin to be commercially important. Workings. All three of the main veins have been ex- plored and prospected, but the principal production of barite was from the Barium Queen mine, which is on the east vein. This mine consists of a drift 310 feet long, a winze 16 feet deep near the face of the drift, and two small stopes, one 16 feet long and 20 feet high and the other 23 feet long and 29 feet high. In addition to the main workings, four open-cuts and two shafts have been dug on the east vein. A shaft about 40 feet south of the Barium Queen mine is 24 feet deep, and another in sec- tion 22, on the north side of the ridge, is about 20 feet deep. The workings on the middle vein consist of four open-cuts and two shafts, 20 to 30 feet deep ; barite has been recovered from the two cuts just south of the stream course near the north edge of the mapped area. The workings on the west vein consist of four small open-cuts and, just south of the ridge, one 20-foot shaft. Reserves. Neither the west vein nor any of the shorter veins in the vicinity contain sufficient barite to be economically important at present ; however, both the middle and the east veins contain appreciable reserves of minable barite. In the middle vein the barite has been uncovered by prospect shafts only .to depths of 20 to 30 feet. Within the east vein barite probably is present from the ridge north of the Barium Queen mine to a depth of at least 200 feet, where it would intersect the pro- jection of the deposit at the level of the mine. In the surface exposures of the veins, however, the barite is not consistent in thickness nor is it continuously exposed ; hence the barite content of the veins at depth cannot be estimated accurately. HANSEN BARITE DEPOSIT AND VICINITY The Hansen barite deposit is 3^ miles northwest of Ludlow, in sec. 30, T. 8 N., R. 8 E., San Bernardino County, California (fig. 1). It is at the extreme south- eastern tip of the Cady Mountains and can be reached by a dirt road that branches from the highway half a mile west of Ludlow. In 1943 the property consisted of four unpatented claims held by Harry Hansen, now de- ceased, of Ludlow. The deposit has been described by Bradley (1930, pp. 54-55) and Tucker and Sampson (1930, p. 298; 1931, pp. 371-372; and 1943, p. 509) in reports of the Cali- fornia Division of Mines. Geology. The rocks in the vicinity of the Hansen de- posit are part of the series of interbedded volcanic rocks, tuff, sandstone, limestone, and siltstone that constitute Special Report 39 the lowest exposed unit of the Tertiary section in the southeastern part of the Cady Mountains, and are thought by Hewett to be Miocene in age (Moore, B. N., Hewett, D. F., et al., 1931, p. 150). The rocks in the immediate area of the barite deposits (pi. 3) consist of olivine basalt flows overlain by volcanic breccias, tuff- aceous sandstones, and conglomerate.* Andesite, though not exposed in the mapped area, crops out and overlies the basalt 4,000 feet to the northwest. The basalt is a brown vesicular and amygdaloidal rock that forms flows 3 to 10 feet thick. It is black on weathered surfaces. The tuffaeeous sandstones overlying the basalt are thin- bedded, bright red to bright green, and 75 to 100 feet thick. Volcanic breccias overlie the sandstones or, where the sandstones are absent, rest directly on the basalt. The breccias are well-indurated, massive-bedded rocks that weather to brownish-black and black cavernous surfaces. They are composed of red, brown, and black basalt and andesite blocks, as much as 5 inches long, in a matrix of ash. The thickest exposed section of the breccias, one in which the top has been eroded and the base is not exposed, is more than 150 feet thick. Quaternary al- luvium overlies the bedrock at the lower altitudes. The structural features of the area are similar to those of the rest of the Cady Mountains. Numerous faults cut the mountains ; one of them has a trend that when pro- jected passes under the alluvium at about 600 feet south of the Hansen mine. This fault, a reverse fault with a southwest dip, is exposed 3,000 feet west of the deposit and can be traced for several miles to the northwest. The small hill in which the deposit lies is cut by many smaller faults, only the most conspicuous of which are shown on the map. Barite occurs as fissure fillings where these faults cut the basalt. Similar barite veins occur in other parts of the Cady Mountains, though none so far observed are thick enough to be economically important. Two fault systems are present : a dominant system with a northwesterly trend within which the strike of the individual faults ranges from N. 10° W. to N. 40° W. ; and a subordinate system of faults that trend N. 10° to 30° E., terminate against, and in some cases, off- set the faults of the dominant system. Several additional faults do not fall within the above systems. The attitude of some of the faults in the dominant system could not be determined, but of those that were measurable all but one dip steeply east. The exception is a fault in the Han- sen mine, which dips 70° W. Some of the small barite veins, which probably follow faults, also dip to the west. Nearly all of the faults of known attitude are normal faults, but important strike components of their displace- ments may exist. The second fault from the west end of section A- A' (pi. 3), probably typical of the larger faults in the mapped area, has a displacement of about 230 feet. Barite Veins. Barite occurs as fissure fillings in both faults and fractures closely associated with these faults at the Hansen deposit. Most of the veins that have not been mined are 1 to 2 inches thick, although a few are as much as a foot thick. Those veins from which barite has been recovered averaged 3 to 5 feet in thickness and locally reached a maximum of 11 feet. The veins are dis- continuous and cannot be traced for more than a few * For a generalized geologic map to the southeastern part of the Cady Mountains see : Durrell, Cordell, Geological investigations of strontium deposits in southern California : California Div. Mines Special Rept. 32, 1953, pi. 8. hundred feet. In some places, such as in the first ravine northwest of the Hansen mine, they are short and closely spaced. The barite in the veins occurs as reddish-brown lamel-fl lar aggregates, with individual plates up to 3 inches in I diameter, coated with iron oxide and quartz. The veins | are in part banded, as shown by different degrees of iron- staining and different crystal sizes that resulted from I two successive periods of deposition. Parts of some veins \ and the adjacent wall rock have been brecciated and are I recemented by iron-stained barite, and as a consequence: basalt fragments are included in the veins. Four main barite areas have been worked, all of which are in or associated with well-defined faults in the basalt. The Hansen mine was developed in the northwest-trend-' ing vein along the most westerly fault at the south end' of the hill (pi. 3). Before it was mined the vein was ex-l posed discontinuously for about 300 feet along the sur- face ; in several places it thinned or tapered out for short, distances. The southeast end was covered by alluvium,', and the northwest end was terminated by a fault. The! thickness and attitude of the vein varied with depth., The richest part, now stoped, averaged 4^ feet in thick- ness, with a maximum of 11 feet, and was exposed fori 120 feet at the surface ; underground, however, the vein dipped more steeply, tapered to 1 foot in thickness, and was followed for only 80 feet. The attitude and size of: the vein were controlled by the fault pattern, and the thickest part of the vein was localized at a flattening of, the dip and a change in trend. Barite fills the next two faults east of the Hansen vein that comprise the second and third barite areas. The vein adjacent to the Hansen vein is exposed for a total length of 70 feet on the surface ; in two shallow trenches it has an average thickness of about 4 inches. The second vein! east of the Hansen vein is discontinuous and crops out' in two main segments. The southeast segment is about 6C feet long and tapers at both ends and with depth. The' width of the vein at the surface is 3 feet, but at the bot-' torn of an exploratory shaft, 50 feet deep, the vein is only* 2 feet thick. The northwest segment of the vein is ex-| posed for 55 feet in an open-cut, where the maximum thickness of the barite is 4 feet. Northwest of this ex-f posure the vein, though discontinuous, can be traced for a distance of 500 feet, but nowhere is the barite more than 1 foot thick, and in most places it is less than half a foot. The fourth area in which the barite has been partly developed is in and near the short spur 700 feet east of the Hansen mine. In the west trench a short vein of barite 1 foot thick is exposed. In and near the other open-cuts to the east a series of small barite veinlets occur in a breccia zone. The maximum thickness of the' barite here is 2 feet, and the length is about 100 feet Barite also occurs in thin short stringers between the two north-trending faults in the east side of the spur. The combined thickness of these veinlets is about 2 feet. Workings. The date of discovery of the barite at this deposit is not known, but most of the development and mining took place between 1927 and 1930. From 1930 to 1952 little work was done, and no shipments of barite have been reported. The main development and recovery have been made along the vein on the southwest side of the hill. A drift was driven along the vein for 210 feet. Barite Deposit Near Barstow 'he vein was then stoped to the surface, a vertical dis- mce of about 50 feet, and a raise was driven from the orthwest end of the drift. A total of 60 carloads of arite is reported to have been shipped from these work- lgs. The stopes are now caved, and the raise is inaccessi- le. A 50-foot inclined shaft was sunk on the vein 100 ;et east of the mine, but little barite was mined. Other lan the above workings, shallow trenches and open-cuts long some of the smaller veins comprise the develop- lent of the deposit. Reserves. The barite in the veins of the Hansen de- osit is siliceous and highly iron-stained ; hence it could e used only for those purposes for which purity is not f primary importance. The thickest and longest vein ;gment, that explored by the workings of the Hansen tine, has already been mined to a depth of about 50 jet. On the floor of the main drift the barite averages feet in thickness for a distance of 50 feet; however, le vein tapers and may pinch out within a few feet elow the drift. The 80-foot vein segment exposed north f the mine contains barite that averages 2 feet in thick- ess. The vein about 100 feet east of the Hansen mine mtains the only other appreciable amounts of barite. 'he southeast segment is about 60 feet long and at the lrface has an average thickness of 3 feet ; the northwest jgment is 55 feet long and 2 feet thick. The southeast ;gment tapers with depth. The total known barite con- ;nt of the above veins is such that the minable reserves £ the deposit are small. BARITE DEPOSITS AT THE LEAD MOUNTAIN MINE AND VICINITY The Lead Mountain mine is about 6 miles east of Bar- ;ow, in sec. 36, T. 10 N., R. 1 W., San Bernardino ounty, California (fig. 1). The mine is on the south side E Lead Mountain and can be reached by a dirt road lat branches from the highway at a point about 2 miles 1st of Barstow. In 1945 the mine was owned by the Pa- fic Base Metals Co., of Los Angeles. Brief descriptions of the mine are given by Tucker 1924, p. 297-298) and Tucker and Sampson (1930, p. 08; 1931, p. 372; and 1943, p. 484) in reports of the California Division of Mines. Geology. Lead Mountain is composed of tuffs, thin iterbeds of sedimentary rocks, and sills of diabase and fenite (pi. 4). Only one of the interbeds, a limestone, is lown on the map. This limestone, a dark-gray to brown orous rock with vague algal structures, is exposed in le southeast corner of the mapped area. The rocks are ertiary and are overlain by small patches of Quater- ary alluvium. The tuff is highly altered, and much of it has been sili- ified. The unsilicified tuff is a soft light-green rock com- osed principally of clay minerals and chlorite with lcluded fragments of quartz-rich rhyolite. The original lastic texture and stratification in the unsilicified tuff re barely recognizable. The silicified tuff is dark red, probably owing to the ;aining by iron oxide introduced at the time of silifica- on. Stratification is more pronounced in this rock. The ilicified rock is composed of a sequence of massive oarse-textured tuffs in beds about 20 feet thick inter- edded with a thick- to thin-bedded tuffaceous sandstone and shale. An interbedded conglomerate about 10 feet thick is exposed in the footwall of the main vein at the east end of the mountain, and thin interbedded red shales are exposed in the tuff at the east end of the mapped area. The combined thickness of the silicified and unsilicified tuffs and interbeds is unknown ; however, about 500 feet is exposed within the mapped area. The age of the tuffaceous beds of Lead Mountain is not known, but the beds closely resemble the tuff members in the lower beds of the Barstow syncline that are gen- erally considered to be Miocene in age. The rocks in the vicinity of the Lead Mountain mine appear to be in a zone of irregular folds, complicated by faulting, and have no pronounced trend, although the rocks both north and south of Lead Mountain trend east- ward. The most important fault of the area is that which contains the main vein. It is exposed at many places along Lead Mountain, and the strike changes from N. 50° W. at the west end of the mountain to N. 25° B. at the east end, where it curves about the south and east sides of the ridge. On the map (pi. 4) the west end of the fault is shown as terminating against a cross fault. Although the main fault is not exposed past this place, it probably continues farther west. The east end of the main fault passes under a cover of slide rock and al- luvium. The main fault is believed to be a reverse fault. A large fault in the southeast corner of the mapped area cuts off a diabase sill. This fault, apparently extensive, cannot be followed farther than is shown on the map. The north side of this fault has moved down relative to the south side. Many smaller faults, including the cross faults offsetting the main vein, are exposed in the area, but only a few of them are shown on the map. Most of the faulting probably took place during or after folding. Barite Veins. Barite occurs as a fissure filling in the main east-trending fault on Lead Mountain and in the related and closely spaced fractures in the hanging wall of this fault. Many small veins that cut Tertiary and older rocks in the vicinity of Lead Mountain, but beyond the area mapped, also contain barite, though not in sufficient quantities to be economically important. The barite along the main vein crops out for 310 feet and before mining was 8 to 18 feet thick. In depth the vein narrowed so that where exposed in mine workings 145 feet beneath the outcrop it was only 2 feet thick. Oxi- dized silver, lead, and zinc minerals associated with the barite were mined from a zone that extended for 120 feet along the vein and may have extended to the same depth as the barite. Barite veins in the hanging-wall fractures are several feet to 30 feet thick, and although these veins thin along the strike, several are more than 400 feet long. The hanging-wall veins dip more steeply near the center of the mountain ; they may converge at depth, as shown in section B-B' of plate 4. The vein along the east-trending fault was formed during several stages of deposition interrupted by re- current movement along the fault. Silicification of the hanging-wall tuff and deposition of massive, fine- grained, brown iron-stained quartz occurred first. The silicified tuff and quartz were shattered and brecciated by subsequent movement along the fault. Resultant fractures, both along the main fault and in the silicified tuff, were filled by coarse-grained, coarsely banded cal- cite colored brown by included iron oxide. The calcite a Special Report 39 is shown on the underground map as brown carbonate vein matter. Again movement occurred, and more exten- sive openings were formed near the center and at the east end of the fault. Barite, in small basal tablets, was then deposited in fine bands along the main fault and in the fractures in the silicified tuff, in some places re- placing the earlier brown carbonate vein matter. Sphaler- ite, galena, and silver minerals, accompanied by small amounts of quartz and calcite, were deposited contempo- raneously with and just after the barite. The vein min- erals then were stained by iron oxide, and the ore minerals subsequently were oxidized. Workings. The Lead Mountain mine was one of the mines in the vicinity of Barstow that were exploited between 1880 and 1890 for silver. After this brief period of activity, it remained idle until 1931, when it was operated for the recovery of barite. Since 1933 it has been inactive. Accessible mine workings consist of an adit, driven from the south side of the mountain, that intersects the vein about 90 feet below the surface, inclined stopes for about 140 feet along the vein that extend to the sur- face, and a 55-foot winze from the bottom of one of these stopes that connects with a raise now inaccessible. The raise is believed to join a deeper adit 250 feet below the bottom of the winze, but this deeper adit is caved. Reserves. Barite is exposed along the main vein for 310 feet and, although the vein narrows with depth, the barite extends for 160 feet down the vein near its cen- ter. Some barite has been mined from the main veil but a considerable tonnage still exists. The barite in the hanging-wall fractures has not yet been exploited. Barite is exposed for several hundred feet along the outcrop of several of the larger fractures and in places averages 10 feet in thickness. Although these fractures probably converge at depth, considerably more barite exists in the fractures than in the main vein; further exploration seems justified. All of the barite is impure. It contains iron oxide, silica, calcite, and minor amounts of oxidized zinc, lead, and silver minerals. The barite may be of commercial value for purposes where purity is not of primary im- portance. SELECTED REFERENCES Bradley, W. W., 1930, Barite in California: California Div. Mines Kept. 26, pp. 45-47. Moore, B. N., Hewett, D. F., Callaghan, Eugene, Nolan, T. B., Rubey, W. W., and Schaller, W. T., 1936, Mineral resources ol the region around Boulder Dam : U. S. Geol. Survey Bull. 871. 197 pp. Tucker, W. B., 1924, Mining in California, San Bernardino County: California Div. Mines, Rept. 20, pp. 199-200. Tucker, W. B., and Sampson, R. J., 1930, Mining in California. San Bernardino Countv : California Div. Mines, Rept. 26, pp. 297-298. Tucker, W. B., and Sampson, R. J., 1931, Mining in California. San Bernardino County : California Div. Mines, Rept. 27, pp. 371-372. Tucker, W. B., and Sampson, R. J., 1943, Mineral resources oi San Bernardino County : California Div. Mines, Rept. 39, pp 484, 508-509. Printed in California state printing office 92840 1-54 2M