EXCHANGE KENTUCKY GEOLOGICAL SURVEY J. B. HOEING, STATE GEOLOGIST IN CO-OPERATION WITH UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR REPORT ON THE PHOSPHATE ROCKS OF CENTRAL KENTUCKY FRANKFORT, KY. 1915 v; THE STATE JOURNAL COMPANY Printer to the Commonwealth Frankfort, Ky. THE CENTRAL KENTUCKY PHOSPHATE FIELD By W. C. Phalen. TABLE OF CONTENTS Page Introduction 1 F'ield work 2 Geography and topography 2 Geology 4 Stratigraphy 4 Description of formations 6 "Wilmore" and Bigby (?) limestones 6 Flanagan limestone 7 Brannon cherty member 7 Woodburn phosphatic member 9 Rocks overlying the Flanagan limestone 11 Structure 11 Discovery of the field 12 The phosphate rock 15 Type of rock 15 Mode of occurrence 16 Distribution and character of the phosphate beds 21 Sections and analyses of phosphate rock 23 Wallace district 23 District west of Midway 29 Frankfort and Forks of Elkhorn district . 31 Lexington district 32 Localities to be prospected 36 Method of prospecting 40 Method of collecting samples 43 The local quarry industry as a guide to prospecting 43 The composition of the phosphate rock 44. Origin ; 46 Source of the phosphate 46 Original mode of occurrence 46 The method of concentration 48 The brown phosphate rock industry 52 General conditions 52 Grades of commercial brown phosphate rock 54 Preparation of phosphate rock for market 55 Removal of overburden 56 Costs of removal of overburden 57 Methods of mining 58 Working cutters 59 The cost of mining phosphate rock 60 Page Washing and drying 61 Conservation of fines 62 The phosphate industry at Wallace, Kentucky 03 Transportation facilities 61 Raw rock phosphate 65 Phosphatic limestone as a source of phosphate 66 The future of low and intermediate grade phosphate rock 67 General remarks 67 Chemistry of process 68 Experimental work in the west 69 Chemical methods 69 Electrical methods 71 The future outlook for Kentucky 74 Bibliography 77 Mohawkian Rocks. Phosphatic area near Midway. Rocks above Mohawkian Geologic Map of Central Kentucky, showing the distribution of Mohawkian (Middle Ordovician) Rocks. Scale: 1 inch=10 miles. THE CENTRAL KENTUCKY PHOSPHATE FIELD By W. C. PHALEN. INTRODUCTION. Tho object of .this report is mainly to present to the public, unfamiliar with Kentucky's resources, data and information of general interest bearing on the phosphate deposits of the State. In it are described the location and geographic distribution, the extent, and relative im- portance of the deposits under present conditions of the phosphate and fertilizer industry, and what may be ex- pected of them as time 'goes on and new processes for working them are developed. The methods of mining and preparing brown rock phosphate for market as practiced in the neighboring state of Tennessee are also briefly outlined, for without doubt Tennessee practice and experience will be utilized when the Kentucky de- posits come to be more generally worked. The element phosphorus is one of the three es- sentials of the commercial fertilizers of the present day. It is supplied to plants in the form of acid phosphate, raw ground rock phosphate, basic slag, and various bone products, such as steamed bone meal, raw bone meal, bone ash, and bone black. Of these various substances acid phosphate is the most largely used. It forms one of the principal ingredients of nearly all commercial fertilizers. It is prepared from the naturally occurring phosphate rock and the essential ingredient in this rock is calcium phosphate which is also often referred to as bone phosphate of lime or bone phosphate, or simply abbreviated to "BPL". Any or all of these terms, which mean the same thing, will be used in this report. Any extensive deposit of phosphate rock in the I 'nited- States is either of present or prospective import- ance. Those in central Kentucky, though not yet worked to any marked extent, occupy a wide territory, are of intermediate grade, and therefore constitute a reserve supply of inportance. They were investigated by the writer in 191.4 and 1915 and the following descriptions summarize the results obtained. This report is primarily an economic report and the geologic features are only considered in the light that they throw on the economic problems involved. FIELD WORK. The field Avork on which this report is based was done in September and October, 19.14, and in June, 1915. It extended over the better known phosphate area lying between the towns of Versailles and Midway, Wood- ford County, especially in the vicinity of Wallace. Con- siderable work was also done west and northwest of Midway, between the Louisville and Nashville Eailroad and South Klkhorn (/reek. Studies were also made in the vicinity of the Forks of Elkhorn Creek, Franklin County, in and around Lexington, Fayette County, and in a few isolated localities which will be mentioned in the subsequent descriptions. The writer gladly acknowledges the efficient help rendered him by Mr. P. B. Winn, of Lexington and Win- chester, Kentucky, in the field work, and also the many valuable suggestions made by Professor A. M. Miller, of the State University at Lexington. References to the work of Miller will be made at the appropriate places in the text. During the course of this work nearly two hundred shallow drillings weie made, the cores carefully sampled, and analyses of the samples together with others were made in the laboratories of the United States Geological Survey by W. 0. Wheeler and E. M. Kanini. GEOGRAPHY AND TOPOGRAPHY. The greater part of the territory discussed in con- nection with the Kentucky phosphate field occurs in the Georgetown quadrangle. This quadrangle comprises a large part of Fayette, Woodford and Scott, and small parts of Franklin and Jessamine counties. Studies were also made in parts of Franklin County off the northwest corner of the Georgetown quadrangle and in the vicinity of Pine Grove Station, Clark County. The phosphate areas within the Georgetown quadrangle in Franklin County have been studied by A. M. Miller* and descrip- tions of the phosphate areas themselves have been pre- pared by A. E. Foerste.f The writer acknowledges the help received from the reports of these geologists and due credit is given to them in the proper places in these descriptions. The low broad hills and the rolling topography are characteristic of this beautiful country, which is of the type known to geologists as a peneplain. The important phosphate deposits occur at the surface of this old pene- plained aica, that is, an area which has long been ex- posed to erosion and which has been worn down to an approximately level surface with most of the broad level hill tops now between 900 and 1,000 feet above sea. The rocks in this section containing the phosphate are entirely limestones. The exposure to weathering of a soluble rock, such as limestone is under ordinary con- ditions, has here brought about fundamental changes in which have been involved the removal of a large part of the country rock. The removal of this rock has been ac- complished both by chemical and mechanical means. Limestone as it usually occurs is mixed with more or less of insoluble hydrous silicates of aluminum (clay). The limestones in this region contain also the insoluble phos- phate rock. The -limestone has been removed, probably largely in the form of the soluble bicarbonate Ca H., (CO*) 2 and the clay left after the solution of the Ca CO 3 hos been carried off, in part at least, mechanically. There is scarcely any doubt that some phosphate rock has been carried off in this manner and thus wasted for all time. In recent times the rate of removal of the residual material, clav and phosphate rock, has been slower than its accumulation, and in some places as revealed in na- tural exposures and drillings, it is 10 or more feet thick. In many other places, of course, the basal limestone out- crops. The principal streams within the areas under dis- cussion are North and South Elkhorn Creeks and their tributary branches. Fortunately South Elkhorn Creek is not too remote to be considered as a possible source of *MiJlpr. Arthur M., Geology of the Georgetown quadrangle; Kentucky Geological Survey. Series 4, Vol. 1, Pt. 1, 1913. po. S17-364. Geology of Franklin County; Ky. Geol. Survey, Series 4, Vol. 2, Pt. 3, 1914, pp. 11-87. fFoerste, A. E. The phosphate deposits in the upper Trenton lime- stones of Central Kentucky; Ky. Geol. Survey, Series 4, Vol. 1, Pt. 1, 1913, pp. SfH-Ui. wash water, great quantities of which are needed in phosphate mills for washing purposes. In a limestone region where sinks abound and where much of the drain- age is below ground, the presence of a stream like South Elkliorn Creek may prove to be of the greatest economic importance to an industry requiring a very cheap and abundant water supply. The topographic and geologic map shows the great paucity of important streams ex- cept South Elkliorn Creek in the neighborhood of the phosphate deposits. The meandering character of the Elkliorn Creeks is pronounced. The presence of streams would be hardly suspected when the country is viewed from a hilltop. Only the dense growth along them indicates their courses. There seems little doubt that the irregular stream courses have been inherited or retained from a period in their history when they flowed over a low broad plain. As the region has been elevated they have cut down or deepened their channels, but this has taken place with few excep- tions along their original courses. Such streams are said to have intrenched themselves, and their meanders are known as intrenched meanders. GEOLOGY. STRATIGRAPHY. The following notes on general stratigraphy and structure of the quadrangle are compiled largely from the reports of Prof. A. M. Miller, as the writer spent less than three months in the area, working chiefly on the economic problems of the phosphate beds alone. The country rocks associated with the phosphate rock deposits are all limestones of different lithology and degrees of purity. The chief foreign ingredients in them are clay, chert, and the phosphate rock itself. They are all of marine origin and belong to the middle part of the Ordovician system; their total thickness is ap- proximately 330 feet. The best stratigraphic section in the vicinity of the area which the writer knows of is on the hill road at the Old Crow Distillery near the mouth of Glenn's Creek. The locality is about 5 or 6 miles w r est of the w^est boundary of the quadrangle. The following illustration (Figure 1) 900- ^^\ ED EM - 32 1 i i 1 1 I L ir:_-J'-' CYAJTH/ANA-38'. -i J __j r ii / I . Jykl^ X - ~ T ~ PRRVV 1 LLE. /O'- i ' i ' [ ' r 1 r ' 1 ' i t i ' iii W O OD B U /? A/ - 39. / i r _ - 11 i s* ^ i i i *"* , i i I ' ' i ' ' l t i BfiAASA/OA, - ft.' J^iA^L -O -V JJ i > J ! i 1 > I l L B/GBY - 7v5T / 1 i t i t i j_ i i i ! ) i i { t 70 _ J L J i l 1 i I i | t t 1 ' \A/// -AA O ft f 7ft i i t i ii i i If i i i i i i ; i J l ' 11 i _ /V EfRM / TA G - 3J " ' T ( A} { . 1 I.. ' 600- i 1 1 1 J ! t CUflOSVILLE- SO. 1 } t t>/x^I j ^ ) 1 1 TYR OA/E - 4 o. 1 1 1 L Lerf-L or GLCMJ C. I f Plectambonites rugosus Cyclonema varicosum Hebertella sinuata Constellaria teres Stromatocerium Columnaria halli Rhynchotrema inaequivalve Stromatocerium reef Rhynchotrema inaequivalve Prasopora simulatrix Dalmanella bassleri layers Fig. 1. Geological section exposed at the Old Crow Distillery from level of Glenn's Creek to top of hill on North Side of the creek, taken along- steep road intersecting the pike at the distillery. (After A. M. Miller.) Ky. Geol. Survey, Series IV, Vol. 1, Part 1, 1913. represents the section at this locality as given by Pro- fessor Miller. The phosphate deposits of the Georgetown quadran- gle occur chiefly in the beds to which the name Woodburn is applied in the section quoted in Fig. 1. These beds, together with the underlying Brannon bed of Miller, correspond to the Flanagan chert of M. R. Campbell in the Richmond folio of the United States Geological Sur- vey. DESCRIPTION OF FORMATIONS. " WILMORE" AND BIGBV ( ?) LIMESTONES. The rocks of this area to which the names Wilmore and Bigby have been applied by Professor Miller con- sist of thin-bedded limestones with some shale between the layers. There is no distinct lithologic or stratigraphic break between them. The name "Wilmore is preoccupied by the Wilmore sandstone member of the Conemaugh formation, and it is therefore quoted in this report. The rocks called Bigby by Professor Miller are correlated by him with the Bigby limestone of southwestern Tennes- see. As this correlation is not established the name Big- by ( ?) limestone is used in this report. The total thick- ness of these formations within the Georgetown quad- rangle is about 90 feet. Of this total thickness 65 to 75 feet belong to the Bigby (?) limestone and the rest, namely 15 to 25 feet, belong to the "Wilmore." Accord- ing to Miller the "Wilmore" is characterized by the brachiopod Dalmanella bassleri and the "chocolate drop" or hemispherically shaped bryozoan Prasopora simulatrix. The Bigby (?) formation contains more abundantly them any other formation the brachiopod Rhynchotrema inaequivalve. Hebertella frank fort en sis, another brach- iopod, is also abundant in the Bigby (?) and upper part of the "Wilmore," reaching its culmination lower down in the section than RhyncHotrema inaequivalve. At the top of the Bigby (I), and confined to a vertical range of not over 10 feet, is a very characteristic assemblage of fossils comprising two bracMopods, Dmprthis ulrichi and Strophomena vicina, a bryozoan of globular habit, Cyphotrypa frankfortensis, and a large coralline fossil Stromato cerium pustulosuni, together with other bryo- zoa. "The coralline fossil Stromato cerium putulosum is usually so abundant at this horizon as to indicate that it formed .a reef in this region in the ancient Ordovician sea." It is especially abundant in the northern part of the Georgetown quadrangle and as far south as the lati- tude of Midway. In places it is as much as 6 feet in thickness and as its top is practically at the base of the next overlying formation (the Flanagan), it has an economic, as well as stratigraphic significance, for the reason that all important phosphate deposits are likely to be found either close above or close below it. Accord- ing to Foerste phosphate rock also occurs locally in the upper part of the Bigby ( .') limestone. FLANAGAN LIMESTONE. The term Flanagan chert was given by M. R. Camp- bell in the Richmond Folio of the United States Geo- logical Survey to the next overlying formation. The term was applied to the rocks occupying the interval between the Lexington and Winchester limestones, the latter terms being practically the same as Linney's Trenton and Hudson formations as used in the latter ? s reports on the counties in the blue grass region for the Shaler and Procter Kentucky State Surveys. According to Miller* only the lower 13 to 15 feet of the Flanagan consists of siliceous limestone which forms chert on weathering. The cherty character is not at all conspicuous excepting as the result of ordinary atmospheric weathering processes where the beds are at the surface. The remainder of the Flanagan con- sists of 30 to 40 feet of thin-bedded, granular, phosphatic limestone. The lower cherty beds are herein called Brannon cherty member, and the upper or phosphatic beds are called Woodburn phosphatic member. BRANNON CHERTY MEMBER. The beds to which Miller has applied the name Brannon in his description of the rocks of the Georgetown quadrangle consist of 13 to 1.5 feet of siliceous limestone which forms chert on weathering. The beds are named for exposures at *Miller, A. M., Geology of the Georgetown quadrangle; Ky. Geol. Sur- vey, Series IV., Vol. 1, Pt. 1, 1913, p. 324. Brannon Station, on the Queen and Crescent Railroad, a short distance south of the southern boundary of the Georgetown quadrangle. These rocks are regarded by Miller, Foerste and Ulricli, as representing the lower or cherty part of Campbell's Flanagan chert. It is the upper part of the Brannon, with its highly contorted or bouldery layers (see PI. 1 and "2) that is so characteristic and it is this portion which furnishes most of the chert at its weathered outcrop. AVhen freshly exposed the Brannon is very firm and hard and requires blasting to remove it. It is a good water bearer and con- sequently its outcrop is generally marked by the pres- ence of springs. The Big Spring at Versailles is at this horizon and also what are known as the Maxwell or Sink- ing Springs at Lexington. The Big Spring at Spring Station is also near this horizon. It is pre-eminently the formation occurring in the numerous sinks found in this quadrangle. This latter association may be due to its tendency to resist temporarily destruction by solution and to form, therefore, the root's of caverns. Later, when brought to the surface by denudation, it goes to pieces rapidly, is decomposed into chert and the roof of the cavern falls and a sink results. There are instances where the collapse of a cavern roof has taken place suddenly and has entrapped grazing stock. As may be inferred from the behavior of this lime- stone under conditions of weathering, natural exposures of the firmer layers are rare. The best exposures are along railroad cuts and in other artificial excavations and in sinks of rather recent development. The Brannon is splendidly exposed in a cut on the Cincinnati, New Orleans and Texas Pacific Railroad (Queen and Crescent route) in Lexington near the Virginia Avenue (Lottie Street) bridge. It is usually a spring horizon and the water comes out directly above the contorted limestone layer which is from 1 to 1% feet thick at this locality. The cherty phosphatic layer shows above the contorted layer, but very little of it is in massive form. (See plate 1.) Near where the photograph was taken the phos- phatic layer is 8 to 1.0 feet thick, but owing to the pres- ence of considerable wash the exact thickness is not readily ascertained. The Brannon resembles a sandy limestone at this locality and thin bands of blue shale up to 2 feet in thick- ness were observed. It is very irregularly bedded a condition especially noticeable where the base of the upper or contorted layer rests on that containing the blue-drab shale. This contact is so irregular that non- conformity or even faulting is suggested. In addition to this locality, eight other localities where the Brannon outcrops are listed by Miller. The Brannon is of interest because in most instances it forms the base of the richest phosphate deposits of this region. WOODBURX PHOSPHATIC MEMBER. The strata to which the name Woodburn has been applied by Miller are described by him as consisting of "about 30 to 40 feet of thin bedded, granular, phosphatic limestone. The name comes from the celebrated Alexander estate, in Woodford County, where the beds are said to be very typically developed, especially as regards their most distinctive feature, the possession of phosphate. The most conspicuous fossil in this formation is the coral, Cohimnaria lialli. It is commonly found in a silicified condition weathered out from its matrix and found loose in the deep, dark red soil formed from the decay of the limestone at its horizon. Another very common fossil in this formation is the very small gastropod Cyclora minula. This fossil occurs only as phosphatic casts of the inside of the shell, and its presence in association with the more phosphatic phases of the rock suggests strongly that the animal which formerly inhabited the shell played an important part in the original segregation of the phos- phate of lime from the sea water. ' ' According to Miller, Foerste and Ulrich, the Woodburn is equivalent to the upper and major part of the Flanagan chert of Camp- bell. At the old workings of the Central Kentucky Phos- phate Company at Wallace, a good opportunity is pre- sented to study the stratigraphic position of the phos- phate rock deposits themselves. From the data which Foerste* obtained he concluded that "the diggings so far made by the Phosphate Company, at their *Foerste, A. E. The phosphate deposits in the upper Trenton limestone of Central Kentucky; Ky. Geol. Survey, Series IV., Vol. I., Pt. I., 1913, PP. 412-413. plant southeast of Wallace, belong- to the upper part of the Benson or Bigby bed, and not to the Woodburn bed. This is confirmed by the latest diggings made at the plant. Here the basal part of the Brannon bed was ex- posed about half way up the hill slope, above the level of the first three strips of phosphate rock, 50 feet wide, so far removed. Here Dinoilldx ubiclil and Stromato- cerium occurred in the upper part of the phosphate rock, beneath the base of the Brannon layer, clearly indicating the geological horizon. The phosphate rock struck northeast of the house 1 on the Steele farm, about a mile and a quarter east of Wallace Station, however, belongs to the upper part of the Woodburn horizon. "It is evident that, locally, weathering away of the Woodburn bed has resulted in the concentration of phos- phatic material at the top of the next underlying lime- stone, which in this case is the Benson or Bigby bed. It is interesting that, at the only locality at which so far any actual commercial development of the phosphate field has been undertaken, the only workable rock so far exploited should belong to the Benson and not to the Woodburn horizon. Aside from this limited area in the neighborhood of Wallace, there are also other localities at which phosphate rock occurs in the upper part of the Benson bed, but by far the greater part of occurrences of phosphate deposits, taking the field as a whole, occur in the Woodburn bed, and this is especially true when the un weathered rock is taken into account. This sug- gests the origin of the most of the phosphatic deposits in central Kentucky in the Woodburn horizons, although locally concentration may have extended downward into the upper part of the Bigby. "The occurrence of StropJiomena vicina in the phos- phatic layers in the upper part of the Stark quarry, a mile and a half south of Wallace, suggests that these layers also belong to the upper part of the Benson sec- tion." The phosphatic rock deposits are proved, therefore, to extend through a considerable stratigraphic interval. It is clear from the descriptions that the phosphate bear- ing beds cannot be represented on the map by a single line, and not very readily by a band as in ordinary geo- logic mapping. The Woodburn abounds in sinks. ~ * 10 ROCKS OVERLYING THE FLANAGAN LIMESTONE. Only the lower member of the formation overlying the Flanagan is of interest or importance in this report for the reason that it occurs close above the phosphate rock horizon and thus may prove of great assistance in helping to locate it. This member is a gastropod horizon. In western Woodford and adjacent parts of Franklin County the shells of gastropods are massed together in a ledge of cherty limestone about 5 or 6 feet thick. In its massive condition this limestone is found in the western and southwestern parts of the Georgetown quad- rangle south of South Elkhorn Creek. Its former pres- ence in the southwestern quarter of the area that is in the region south and west of South Elkhorn Creek- may be readily traced by means of its outliers and the abundance of gastropod chert debris found in the soil. The latter on account of its resistant character may even be found over areas from which the formation has long been removed by weathering, if it ever existed in these parts. Where it occurs as a distinct horizon the phosphate rock bed should be looked for below it on the hiils. STRUCTURE. The area of the phosphate deposits is on the western flank of the Cincinnati geanticline a broad, low dome toward the center of which the rocks outcropping be- come lower and lower in the geological time scale. The rocks in this region, therefore, dip from west to north- west at very low angles so low that the dips cannot be determined instrumentally, that is with a clinometer, but must be reckoned over broad areas on the basis of actual elevations on particular beds. The average rate of this dip is about ten feet per mile and the main streams fall at approximately the same rate in the same direction, thus running over approximate dip slopes. It follows, therefore, that the highest lands are found in the south- east part of the region and the lowest in the northwest. The relief in the Georgetown quadrangle is about ;>50 feet, the difference between 1050 feet along the Nicholasville pike in the southeastern part of the Georgetown quad- rangle, and 700 feet, the approximate elevation of South Elkhorn Creek where it leaves the quadrangle. 11 The uniformity of dip to the northwest has been interfered with in places by disturbances which have re- sulted in faults. Most of these are of slight vertical throw and of limited extent in surface outcrop. They are "tension or normal 77 faults and have a wide drag zone, for which reason the stratigraphic throw is great compared with the vertical. Most of those located occur in pairs, one of which may be considered the primary and the other the secondary or compensating fault. An illustration of other minor movements in the rocks is shown in Plate III. The faults so far as known do not involve those areas where the important phosphate de- posits are found. DISCOVERY OF THE FIELD. There seems to be no question but that the distinc- tion of having called attention to phosphate in the lime- stones of central Kentucky belongs to Dr. Eobert Peter, Chemist of the Kentucky Geological Survey, under the administration of N. S. Shaler. This w r as done as early as April, 1849, in the Albany Cultivator of New T York.* It was Dr. Peter also who first pointed out the associa- tion of phosphate and cyclora and the dependence of the soils of the blue grass region for their fertility on the presence of phosphate rock. In the report by Dr. Peter to State Geologist Shaler, dated February, 1877, there is given the analysis (No. 1778) of a phosphatic limestone from McMeekin 7 s quarry (see Plate IV.) on the Newtown pike, 3 miles north of Lexington. The specimens were collected by Dr. Peter himself and the phosphate layer was reported by the quarryman to be as much as 1 foot thick. The rock is described as being somewhat friable, of a bluish gray color, but brownish gray on the w r eathered surfaces, as containing many microscopic marine univalve shells and as adhering strongly to the tongue. The phosphates in this limestone were found to contain as much as 31.815 per cent, of the weight of the rock of phosphoric acid, which is equivalent to 69.452 per cent, calcium phos- phate. *Ky. Geol. Survey, Chemical Analyses A, Part I., 1890, p. 246. Ky. Geol. Survey, Chemical Analyses A, 1877, pp. 65-66. Also described as Vol. 4, new series, Reports Geol. Survey of Ky., pp. 65-66. 12 The composition of the sample was as follows : Analysis of the Fayette County Phosphate Rock, Dried at 212 F. Phosphoric acid, lime, magnesia, alumina, and iron oxide 85.270 Calcium fluoride not est Carbonate of lime 9.180 Carbonate of magnesia .371 Silica and insoluble silicates 4.780 Alkalies, organic matter, etc., not estimated 3.99 100.00 In his observations on this rock, Dr. Peter makes the significant statement "the subject is worthy of further investigation, especially in view of the agricul- tural and commercial value of the phosphate for use as fertilizers. As is well known, the abundant phosphates of the rock substratum is one of the main causes of the great and durable fertility of our blue grass soil so-called, as well as of the superior development of the animals reared and nourished on its products." At the time the specimen of phosphatic limestone whose analysis is given above was collected, the quarry was not in use and the statement that the layer of rich phosphatic rock was as much as a. foot thick could not be verified. When the quarry was again opened and worked for turnpike material in 1877, a more complete examination was made by Dr. Peter with the following results : Phosphatic Limestone From the McMeekin Quarry, Northwest Side of Newtown Turpike, 3 Miles North of Lexington, Taken From Irregular Layers About 1 Foot in Thickness. Composition Dried at 212 F. Lime carbonate 49.160 Magnesia carbonate .090 Phosphates, with AIX^FeAi, etc. (containing 21.018 per cent, phosphoric acid) 46.540 Siliceous residue 2.820 Organic matter and loss 1.390 100.000 13 The analyses given above and others indicated an ir- regular distribution of phosphate, and so 11 other samples were selected from portions of the phosphatic layer. The quantity of phosphoric acid (PoO.-,) in these 11 samples varied from 5.053 per cent, to 21.940 per cent., and averaged 15.89(3 per cent., pointing to an ir- regular distribution and an irregular local origin. Interest in the occurrence of phosphate rock and phosphatic limestone in Kentucky did not develop at once, or at least lead to further field exploration or in- vestigation. The discovery and the commencement of work in the Tennessee phosphate field in 1894-1895 quick- ened interest in phosphate rock deposits in general. The association of calcium phosphate layers at the top of the so-called Tienton limestone near Lexington with cer- tain organic remains was pointed out by A. M. Miller as early as February, 1896.* During the summer of 1904, Miller was engaged in field work for reports on the geo- logy of Jessamine, \Voodford and Franklin counties. These reports, except that for Franklin County, were never published, but in that on "YToodford County he re- ferred to the phosphate deposits and their exceptional richness at the top of the so-called Trenton in the terri- tory between Midway and Versailles. In a report by the former director of the Kentucky Geological Survey, Charles J. Norwood, f it is stated that "Professor Miller discovered the exact representa- tive of the rock phosphate beds of Mt. Pleasant, Tennes- see, some examples running* as high as 72 per cent, phos- phate, and having* definitely differentiated them, he was able to trace them over considerable areas." Thus the fundamental studies made by Professor Miller entitle him to the credit of suggesting the possibilities of this region as the site of potentially important phosphate rock deposits. $ *Miller, A. M. The association of the gastronod e-enus cvclora with phosphate of lime deposits. Am. Geol., Vol. XVII., 1896, pp. 74-76. fKy. Geol, Survey Kept, on 'the progress of the survey for the years 1904-1S05, pp. 25-26. tit has been stated that in the summer of 1915, a negro while digging- post holes on the farm of H. L. Martin, near Midway, discovered what he considered nhosphate rock, similar to the brown phosphate rock in Tennessee. Mr. Martin verified the negro's oninion. See Gardner, James H., Mins and Minerals, November-. 1912. p. 207: Waggaman, W. H., U. S. Dept. of Agriculture, Bureau of Soils, Bull. No. 81, Marcli 20, 1912, p. 24. 14 THE PHOSPHATE ROCK. TYPE OF BOCK. Phosphate rock occurs in a variety of ways and has been designated by a variety of names in the different states where found. The Ordovician phosphate rock of central Kentucky belongs entirely in a class known as brown phosphate rock, first so-called in middle Tennes- see. It occurs as a distinctly laminated residual deposit, al^o as filling solution cavities or pockets in a more or less phosphatic limestone. (See Plates V. and VI. and Figure 4.) The rock itself occurs in porous or loosely coherent plates and whore exposed, naturally or artificially, these plates vary in thickness from the very thinnest up to those a few inches thick. The more massive rock is re- ferred to as lump, plate, or hard rock. The latter may also occur in thick heavy slabs of several inches, or even a foot or moie in thickness. This massive type is not common in Kentucky. It was observed in a natural ex- posure on the Louisville Southern Railway near the Cahill place, about a mile and a half west of Lexington and on the Harkness estate (Walnut Hall) east of Cane Bun and near the Fayette-Scott county line in the north- east nart of the Georgetown quadrangle. Doubtless it is found in many other places that were not seen. Usually the plates or slabs are separated from each other by layers of loosely cemented or porous material consisting of phosphate rock in a fine state of division mixed with more or less clay. The explanation of this form of rock will be made clear under descriptions of origin. The material is termed phosphate muck and is found between individual plates, especiallv in fresh ex- posures or drill holes. Muck, or the soft mixture of phosphate and clay, often is found just above the lime- stone on which the phosphate rock stratum rests. There is also another form of brown rock known as phosphate sard, some of which is very rich in cilcium phosphate and is therefore of commercial value. Mix- tures containing varying proportions of plate rock, sand rock, and muck constitute what is included under the term brown phosphate rock. The color of the rock varies from a drab through a grayish and yellowish brown to a deep brown or almost 15 black. The muck layers so often found overlying the limestone at the bottom of the numerous holes drilled by the writer, are usually nearly black, and in some cases it was thought that the dark color might be due to the presence of hydrous oxides of manganese which are a very common constituent of the soils in the blue grass region. The thickness of the beds will be described under mode of occurrence. MODE OF OCCURRENCE. Brown rock phosphate deposits depending on their manner of occurrence, have been designated as "blanket" and "collar" deposits/* The latter have also been called Fig. 2. Blanket phosphate deposit on low, flat hill. Showing the development of "horses" and "cutters." Fig. 3. "Collar" or "run" phosphate deposits formed on steep hillside. "hat band" or "rim" deposits. The name suggests the character of the formation. The term "blanket" applies to the nearly horizontal deposits of considerable areal extent, while those designated "hat band" or "rim" occur within a limited vertical zone on the hillsides. (See Figures 2 and 3.) The character of the deposits depends *Hayes, C. W., U. S. Geol. Survey, Folio No. 95, 1903, pp. 5-6. 1G on the topography or lay of the land; and it is obvious that the blanket deposits are the most extensive, and with other conditions the same, are the most valuable. It is also obvious that there cannot be any sharp or ar- bitrary division between blanket and collar deposits, but that the one type may merge imperceptibly into the other. At the old workings of the Central Kentucky Phos- phate Company, the predecessor of the United Phosphate & Chemical Company, near Wallace, there are good il- lustrations of the collar type merging into the lolanket type of deposit. The workings here are not very exten- sive, at least not enough to indicate to one who has not prospected the area, whether the deposits cover the entire hill where w r ork has been done and hence belong strictly to the blanket type. The drilling done in the course of this investigation, and the information gathered from talking with land owners who are acquainted with conditions from local drilling, seems to indicate that the deposits belong to both the collar and blanket types, and that the former are probably the more numerous. It was stated above that the type of the deposits depends on the topography. The topography in this part of Kentucky is gently undulating, or rolling. A study of it shows clearly that it has resulted from the dissection, or cutting down of a gently sloping surface which orig- inally was more than 1050 feet high in the southeastern part of the Georgetown quadrangle, and more than 850 or 900 feet high in the northwestern corner. Such topog- raphy affords the best conditions for the formation of residual phosphate deposits, providing the other requi- site conditions are fufilled. The Lockport quadrangle to the northwest furnishes an example where geological conditions are similar to those in the Georgetown quad- rangle, but where the topography is such as to preclude the possibility of the formation of phosphate rock de- posits owing to its rugged character, except at the very outcrop. It follows, therefore, that the economic im- portance of such deposits should be slight. The phosphate rock deposits are always associated with limestone and it is from a phosphate bearing lime- stone that they are considered to be derived. The orig- inal phosphatic material occurs in definite bands in the 17 limestone mixed with calcium carbonate. (See Plate VII.) It is believed without much doubt that these highly phos- phatic bands are original, and that they were laid down alternately with bands of limestone containing less phos- phate, or none at all. With the leaching of the limestone the insoluble phosphate rock and the other insoluble materials orig- inally present, which are chiefly clay, silicified fossils, and chert debris, have slumped down slowly onto the underlying limestone. The capping of clay has resulted from the similar changes which have taken place in higher clay bearing or argillaceous limestone beds. In the writer's opinion no other theory or hypothesis is re- quired to explain the formation of the phosphate de- posits. Solution has taken place along joint planes more rapidly than in the other places and has led to the formation of so-called "cutters" or "horses." (Plate IX.) Horses are the limestone masses projecting into the phosphate rock layers, the latter of which curve over them in arches, as will be observed from the illustrations (Plates V. and X.) and in the cutters between the horses the phosphate rock deposits often show abnormal thickness from the mechanical slumping down from the flanks of the horses. (Figure 4.) This behavior of the phosphate rock leads to great variations in the thickness of the deposits and necessitates most thorough prospect- ing before the average thickness over a given area can be closely estimated. Splendid examples of the irregular limestone surface underlying the phosphate rock are to be seen at the old workings near Wallace (Plate IX.), and in sections at many quarries in the region, among which may be mentioned the Haggin quarry at Elmen- dorf, east of Maysville pike; the Stark quarry on the Versailles-Midway pike; the James P. Headley quarry just outside of Lexington city limits and east of the Russel Cave pike, and doubtless at many other quarries over the entire region. Actual exposures of limestone and overlying phos- phate are not very common. The mode of occurrence, therefore, cannot be studied as closely as desirable from the commercial point of view from either outcroppings or quarries. Drilling operations and the digging of pits are necessary to throw the maximum light on the mode 18 I . 1. r- r^-r t . 1 "J T r~r i . .1 iLS I >. I . r "_;" ' t ''^^j^g^m'lg Fig. 4. C Clay -seam. S Soil. L.S. Limestone. J Jointing. P Phosphate. DEVELOPMENT OF CUTTERS. Scale 1 inch=20 feet approximately. Showing the development of cutters after J. S. Hook, "The Resources of Tennessee." Vol. IV, No. 2. April, 1914. P. 64. of occurrence. The former method of prospecting will be described under the proper heading. The overburden of the phosphate rock consists, as has been stated, chiefly of clay mixed with different ma- terials like chert debris, silicined fossil remains, etc. This overlying soil contains small quantities of lime phos- phate. The following section was measured on the Louis- ville Southern Railway near the Cahill place already referred to as about 1V> miles northwest of Lexington: Section of Phosphate Rock on the Louisville Southern Railway Near the Cahill Place, 1'/ 2 to 2 Miles Northwest of Lexington. . 4' .Overburden. 3' 6" Massive phosphate rock. 3' 9" Clay. 3' 6" Limestone and blue shale. A sample of the overburden gave less than 2 per cent, phosphoric acid. A sample of overburden from station No. 11, near Hulett's, gave less than 1 per cent, phosphoric acid. A sample collected from a thickness of S 1 /^ feet in excavating for a telephone pole at the road- side : >4 of a mile northwest of Hillenmeyer Station, gave less than 2 per cent, phosphoric acid. Though the over- burden contains but little phosphate, its possibilities as a filler in making commercial fertilizer ought not to be lost sight of, for it is this soil that renders the blue grass region so productive. The abundance of iron and manganese oxide con- cretions in the soil overlying the phosphate rock is worth remarking. A notable quantity of these concretions oc- curs near Station No. 11, or Hulett's, on the interurban trolley line between Lexington and Nicholasville. Here a layer of the concretions 3 feet thick was observed. The top soil in the entire blue grass region is shot through with manganese concretions, usually of small size. These, no doubt, were originally disseminated in the limestone and have been segregated during the process of weather- ing. The presence of manganese is of interest since it has been considered to have some fertilizer value. An elaborate series of experiments has been carried on by the Bureau of Soils, IT. S. Department of Agriculture, 20 having in view the determination of the effect of man- ganese salts on grain and vegetable growth. Both pot and field tests were made and the conclusion was reached that crop growth in unproductive sandy loam was stimu- lated by the addition of 5 to 50 parts of manganese to a million of soil, whereas no effects were noticeable when a productive loam soil was used. In some tests an actual decrease in yield was attributed to the addition of man- ganese salts.* DISTRIBUTION AND CHARACTER OF THE PHOSPHATE BEDS. A somewhat restricted district in the vicinity of AVallace a few miles south, southeast, and southwest of Midway, Woodford County, is the only one of promi- nence within which phosphate rock is known to occur to any great extent. Between Midway and Spring Sta- tion, along the Louisville and Nashville Railroad, and on certain farms to the north of the railroad, is another area where phosphate rock has been found in some quantity. The limits of these areas have not been very accurately determined, but enough drilling has been done to indicate that locally, very important deposits of phos- phate rock should be expected. When it is recalled that brown rock phosphate may be expected to run from 600 to 1,000 tons per acre per foot of thickness, small acre- ages may prove of great importance if the phosphate deposits are thick enough and of good quality. In the fields and districts named there are many small areas in which the phosphate bed is lacking, or too thin to be of value, or perhaps is overlain by a cover too thick to remove profitably. Some prospecting has been done throughout all the areas and the distribution of the phosphate is quite well known in certain tracts. The work has been done privately, and hence the records are not available. As an example of the quantity of phos- phate rock occurring in this region, it has been told the writer that 16,000 to 18,000 tons of phosphate rock were produced from a five-acre tract at "Wallace, that is to say an average of 3,600 tons per acre. It has also been stated that 1,200 to 1,400 tons per acre foot are found i rer, J. J. and Sullivan, M. X. The action of manganese in soils, U. S. Dept. of Agriculture, Bull. 42, 32 pages, 1914. 21 in this region, and the excess over that usually occurring in the Tennessee brown rock field is due to the greater hardness and density of the Kentucky rock as compared with that in Tennessee. For the accuracy of these figures and statements the writer cannot vouch. Outside of the Wallace area and that to the west of Midway, phosphate rock is known to occur in and around Lexington, Fayette County. Phosphate rock deposits are also known in the vicinity of Georgetown, Scott County, near the Forks of Elkhorn, Franklin County, near Ver- sailles, Woodford County, and near Pine Grove Station, Clark County. The results obtained from prospecting in these different areas are outlined beyond and com- ments made as appears necessary. In this report the Wallace area will be understood to include the area between Midway on the north and Versailles on the south, with Wallace as a geographical center. It will comprise the territory between South Elkhorn Creek on the east and an indefinite boundary west of the Versailles and Midway pike. It was near Wallace a short distance to the east of it and near the Georgetown- Versailles branch of the Southern Railway that the first phosphate of the Kentucky field was mined and sold. The low rolling topography of this region af- fords ideal conditions for the development of commercial phosphate deposits, assuming its original presence in the limestone. The region is also notably fertile and in the district along the Midway- Versailles pike the name "as- paragus bed" of the blue grass region has been applied, owing to its marked degree of fertility. " The following sections, together with the map, show the general distribution of the phosphate rock together with its character, variations, and composition as deter- mined chiefly by prospecting with the drill. All sections and analyses numbered 100 or over re- fer to drill records and the samples obtained from them. 22 SECTIONS AND ANALYSES OF PHOSPHATE ROCK. Wallace District. No. 8. Central Kentucky Phosphate Co., y 2 mile east of Wallace Crossroads, Woodford County, Ky. No. 9. Central Kentucky Phosphate Co. No. 10. Central Kentucky Phosphate Co. No. 11. Central Kentucky Phosphate Co. No. 12. Central Kentucky Phosphate Co. No. 8 4 y 2 ' Overburden. 2V 2 ' Phosphate rock, 59.78% Ca 3 (PO 4 ) 2 . Limestone. No. 9 6 y 2 ' Overburden. 4' Phosphate rock, 65.25%Ca,(PO 4 ) 2 . Limestone. No. 10 iy 2 ' Overburden. 2 1 / 2 ' Phosphate rock, 71.88% Ca 3 (PO 4 ) 2 . Limestone. No. 11 6' to 7' Overburden. 2'-7" Phosphate rock, 72.86% Ca 3 (PO 4 ) 2 . Limestone. No. 12 12' to 13' Overburden. 5 '-7" Phosphate rock, 72.85% Ca 3 (PO 4 ) 2 . Limestone. No. 20. R. S. Stark quarry, east side Versailles-Midway pike, 3% miles southwest of Midway, Ky. 2'-4' Overburden. 2' Phosphate rock, 66.48% Ca 3 (PO 4 ) 2 . Limestone. No. 22. R. S. Stark quarry, east side Versailles-Midway pike, 3^ miles southwest of Midway, Ky. 5' Overburden. 4' Phosphate rock, 58.55% Ca 3 (P0 4 ) ? . Limestone. No. 23. Clinton M. Hawkins farm, 3 miles southwest of Midway, or y 2 mile south of Wallace, Woodford County. 1' 6" Overburden. 1' 6" Phosphate rock, 59.88% Ca 3 (PO 4 ) 2 . Limestone. 23 No. 100. S. C. McKinnivan estate, 1 mile southeast of Wallace. 10' Clay overburden with chert. 1' Phosphate. rock, containing 17.79% Ca^PO,),. Limestone. No. 104. S. C. McKinnivan estate, 1^4 miles southwest of No. 100. 7'..... .Clay. 2' 1" Low grade phosphate rock. 6' 3" Phosphate rock, lower part of which is brown phos- phate muck. Limestone. Analyses- No. 104. 2' 1" layer. 31.86% Ca :i (P0 4 ),. No. 104A. Highest grade material in drilling. 53.47% C'a :t (PO,),. No. 104B. Muck from lower part of drilling. 49.04% Ca 3 (PO 4 ):,. No. 101. Will Steele's estate, south side Frankfort and Lexington pike, 114 miles southeast of Wallace. 1' 10" Clay. 0-8" Phosphatic Clay. 3' 9" Phosphate rock, 48.46% Ca 3 (PO 4 ),. Limestone. No 102. Will Steele's estate, 14 mile south of No. 101. 3' 4" Clay. 10' 4" Phosphate rock, 48.06% Ca,(PO 4 ),. Limestone. A grab hand sample selected from the core drilled showed 48.18% Ca 3 (Po 4 ) 2 . No. 103. Will Steele's estate, ^ mile west of No. 101. 4' 5" Clay. 2' 2" Phosphatic clay and low grade f Upper 2' 2", 53.47% phosphate Ca 3 (P0 4 ) 3 . 5" Phosphate rock I Lower 5", 65.16% Limestone. Ca 3 (P0 4 ),. No. 105. R. S. Stark estate, 1% miles southeast of Wallace, north of Frankfort and Lexington pike. 2' 7" Clay. 2' Phosphate rock containg sand and clay, becoming clay at base, 31.49% Ca 3 (PO 4 ) 2 . 2' 11" Clay. Limestone. No. 106. R. S. Stark estate, % mile north of No. 105. 6' 5" Clay. No phosphate rock. Limestone. No. 107. R. S. Stark estate, % mile northwest of No. 105. 4" 6" Phosphate rock 5 Upper half ' 42 ' 92% Ca ' (PO ' ) " Limestone. < Lower hal( ' 23 ' 80% 24 No. 108. Estate of the late Mrs. Margaret Murray, 1% miles southeast of Wallace and north of Frankfort and Lexington pike. 9' Clay. 7' 8" Phosphate rock. 2' Clay and some phosphate. Limestone. Three different grades of phosphate rock came from this drilling containing 31.47%, 41.46%, and 63.87% Ca.CPOJ,, the latter from a 2' 10" layer overlying the 2' clay bed. No. 109. Estate of the late Mrs. Margaret Murray, % mile northwest of No. 108. 2' 10" Clay. 1' 5" Chert. 1' 10" Clay and chert. 3' 6" Phosphate rock. Limestone. Two different grades of phosphate rock came from the hole, con- taining 54.48% and 54.06% of Ca 3 (PO 4 ),. No. 110. Estate of the late Mrs. Margaret Murray, 1% miles east of Wallace, near corner of farm. 11' 4" Clay. 4' Low grade phosphate rock. Limestone. Two different grades of phosphate rock came from the hole, con- taining 21.30% and 30.40% Ca,(PO 4 ) 2 . No. 111. Estate of the late Mrs. Margaret Murray, 580 feet south of No. 110. 3' 5" Clay. 2' Phosphate rock. Limestone. Three different grades of phosphate rock came from the hole, con- taining 20.30%, 37.62%, and 20.43% Ca 3 (PO 4 ) 2 . No. 112. Henry L. Martin estate, % mile east of Wallace, north of Frankfort-Lexington pike. 8' 9" Clay. 2' 9" Phosphate clay. 3' 2" Phosphate sand, 50.30% Ca 3 (P0 4 ) 2 . 3' 9" Sand and plate rock, 60.87% Ca 3 (PO 4 ) 2 . Limestone. No. 114. H. L. Martin, Jr. estate, % mile south of house. 1' 11" Clay with phosphate rock at base. 4" Phosphate rock, 25.78% Ca 3 (PO 4 ) 2 . Limestone. No. 115. Gate to H. L. Martin, Jr. estate, l 1 /^ miles southwest of Mid- way. 12' 8" Clay. 4' 2" Phosphate rock, 37.43% Ca 3 (PO 4 ) 2 . Limestone. 25 No. 116. H. L. Martin, Jr. estate. 5' 11" Clay. 3' 1" Phosphatic sand, 35.16% Ca 3 (PO 4 ) 2 . 3' 9" Clay and phosphate rock, 44.30% Ca 3 (PO 4 ) 2 . 3' 1" Phosphate sand and plate rock, 56.50% Ca 3 (PO 4 ) 2 . Limestone. No. 118B. H. L. Martin, Jr. estate, % mile south, 15 E. from the rail- road crossing. 2' 7" Clay. 11" Phosphate rock, 56.19% Ca 3 (PO. 4 ) 2 . Limestone. No. 119. H. L. Martin, Jr. estate. 6' 2" Clay. 2' 1" Phosphate rock, 43.53% Ca 3 (PO 4 ) 2 . Limestone. No. 120. H. L. Martin, Jr. estate, N. 10 E. from the house. W T 11" Phosphate rock ...... \ Upper 3 ' "' 28 ' 92% <*<>.),. Limestone. 1 Lower 4 ' U * 40 ' 62% Ca < No. 121. H. L. Martin, Jr. estate. 5' 1" Clay. 3" Phosphate rock, 40.19% Ca 3 (PO 4 ),. Limestone. No. 122. H. L. Martin, Jr. estate, % mile northeast of No. 121. 4' 4" Clay. 3' 5" Phosphate rock, 50.20% Ca 3 (P0 4 ) 2 . Limestone. No. 123. H. L. Martin, Jr. estate, % mile southeast of house. o' Q" Clav 3- 3" Phosphate rock ....... \ U <"> er r 31 ' 06% Limestone. I Lower r 10 ' 22 ' 20% Ca < PO '>" No. 124. H. L. Martin, Jr. estate, east of Versailles and Midway pike, about % mile southwest of Midway. 8' 6" Clay. 6' 3" Phosphate rock; lower 4' 7" gave 34.38% Ca 3 (P0 4 ) 2 . Limestone. No. 125. H. L. Martin, Jr. estate. 5' 9" Clay. 2" Phosphate rock, 24.36% Ca 3 (P0 4 ) 2 . Limestone. No. 126. James J. Nugent, just northeast of Wallace crossroads. 7' 5" Clay. 11' 9" Phosphate rock. Limestone. The three grades of phosphate rock from this drilling ran as fol- lows: Phosphate sand 8", 31.96%; phosphatic clay 3' 2", 43.34%; and phosphate rock, T 2", 54.25% Ca 3 (PO 4 ) 2 . 26 No. 127. Nugent Bros, estate, y 2 mile south of Wallace crossroads. 8' ...Clay. V 3" Phosphate rock ........ .( U er 4 ' 10 "' 45 ' 00 % Ca.(PO.),. Limestone. ( Lower 3 ' 5 "' 65 ' 92% Ca 45 ' 13% CMPOJ, Limestone. ( Lower 2 ' 8 "' 36 ' 27 % Ca,,(PO 4 ) = . No. 133. E. L. Lillard estate, % mile west of No. 132. 7' 6" Clay. 4' 2" Phosphatic clay, 24.56% Ca 3 (PO 4 ) 2 . 3' 2" Phosphatic sand and plate rock, 36.78% Ca 3 (P0 4 ) 2 . 3' 3" Phosphatic sand and plate rock, 48.34% Ca 3 (P0 4 ) 2 . Limestone. No. 134. E. L. Lillard estate, % mile northwest of No. 133. 3' 4" Clay. 5' 2" Phosphate rock, 33.11% Ca 3 (P0 4 ) 2 . Limestone. No. 136. E. L. Lillard estate, 3 miles southeast of Midway. 3' 6" Clay. 3" Phosphate rock, 52.23% Ca 3 (PO 4 ) 2 . Limestone. No 138. E. L. Lillard estate, % mile west of Zion's Hill near South Fork of Elkhorn. 3' .............. Clay. 1' 4" Phosphate rock, 39.82% Ca 3 (P0 4 ) 2 . 5' .............. Phosphatic clay, 15.82% Ca 3 (P0 4 ) 2 . Limestone. 27 No. 137. J. B. Sellers estate, 2 miles southeast of Midway near high- way. 8' Clay. ...... 6' 2" Phosphate rock ...... ( V * r V 5 "' 48 ' 67 % Ca s (PO 4 ) 2 . Limestone. \ Lower 4 ' 9 "' 37 ' 69 % Ca(PO 4 ) 2 . No 144. R. S. Stark estate, just east of Versailles-Midway pike, iy 2 miles southwest of Wallace, opposite old quarry. 8' 1" Clay. 14' 4" Phosphate rock, 50.77% Ca 3 (PO 4 ),. Limestone. No. 145. R. S. Stark estate, 25 feet west of hole No. 144. 3' 5" Clay. V 2" Phosphate rock, 71.64% Ca 3 (PO 4 ) a . Limestone. No. 146. R. S. Stark estate, l 1 ^ miles south of Wallace, near Southern R. R. 5' 7" Clay. 1' 5" Low grade phosphatic material, 41.32% Ca,(PO 4 )o. Limestone. No. 147. R. S. Stark estate, % mile southeast of No. 146. 1' 10" Clay. 2' 8" Phosphate rock, 57.06% Ca :( (P0 4 ) 2 . 1' 6" Clay and chert. 4' 2" Clay. Limestone. No. 148. R. S. Stark estate, y 2 mile northeast of No. 147. 2' 2" Clay. 3' 3" Phosphate rock, 53.10% Ca 3 (P0 4 ) 2 . 8' ........ Dark brown clay, 29.50% Ca^PO,),. Limestone. No. 150. Lister Witherspoon, iy 2 miles southwest of Wallace and west of Versailles-Midway pike. 4' 5" Clay. 3' 1" Containing some phosphatic sand merging into clay at base, 23.26% Ca 3 (P0 4 ) 2 . Limestone. No. 156. Lister Witherspoon estate, rear of residence. 5' 6" Clay. 1' 4" Phosphate sand and clay; this and the 2' 1" layer be- low gave 16.11% Ca 3 (P0 4 ) 2 . 11" Cherty material passing into clay gumbo. 2' 1" Phosphate rock and clay. Limestone. No. 151. McBrayer Moore estate, 1 mile southwest of Wallace. 6' 10" Clay. No phosphate rock. Limestone. 28 No. 152. George McLeod estate, 2% miles southwest of Wallace. 2' 5" Clay. 8" Containing some phosphate sand, no analyses. Limestone. No. 155. George McLeod estate, in front of house near sink hole. 15' 4" Clay. 2' 3" Phosphate sand, 33.55% Ca 3 (P0 4 ) 2 . Limestone. No. 159. Estate of Thomas Dunlap, 3 miles S. B. of Wallace, north side of Frankfort and Lexington pike. 2' 2" Clay. 1' 4" Phosphate muck, 33.09% Ca 3 (P0 4 ) 2 . Limestone. A sample of phosphate rock collected from a 3' 6" bed exposed in excavating a barite vein near gate to farm gave 52.49% Ca. (PO 4 ) 2 . No. 161. Estate of Wm. A. Dunlap, 2V, miles S. E. of Wallace, near South Elkhorn Creek. 1' 11" Clay, the lower part of which contains phosphate rock fragments. 1' 6" Clay and some fragments of high grade phosphate rock. 1' 11" Phosphate muck, probably low grade, 35.45% Ca :; (PO 4 ) 2 . Limestone. No. 162. Estate of Wm. A. Dunlap, 2 miles east of Wallace. 3' 10" Clay. 1' 7" Fine phosphate sand. 3' 4" Phosphate muck and phosphate sand, 42.01% Ca.CPOJo. 4' 5" Low grade clay. Limestone. District West of Midway. No. 142. Estate of Mrs. Chas. Nuckols, 1% miles northwest of Midway. 4' 10" clay. 1' 6" Phosphate rock. Limestone. The two grades of phosphate rock from this hole gave 52.43% and 48.16% Ca 3 (P0 4 ) 2 . No. 143. Estate of Mrs. Chas. Nuckols, 14 mile north of No. 142. 8' 8" Clay. 4' Phosphate and clay, rather low grade, 37.56% Ca ; .(P0 4 ) 2 . 2' 2" Phosphate sand, 51.13% Ca 3 (P0 4 ) 2 . Limestone. The two grades of phosphate rock from this hole gave 37.56% and 51.13% Ca.,(P0 4 ) 2 . No. 139. E. L. Davis estate, Rookwood Station, on L. & N. R. R., 1% miles N. W. of Midway. 2' 2" Clay. V 10" Phosphate rock, 40.35% Ca 3 (P0 4 ) 2 . Limestone. 29 No. 140. E. L. Davis estate, % mile N. E. of No. 139, on railroad. 5' 3" Clay. 4' 3" Phosphate rock and sand, 64.30% Ca 3 (PO 4 ),. 10" Clay and plate rock, 37.90% Ca 3 (PO 4 ) 2 . 1' 8" Clay. Limestone. No. 141. E, L. Davis estate, on L. & N. R. R., in small sink y 2 mile S. W. of No. 139. 11' .Clay. 4' 8" Phosphate rock j U ^ er *'' 35 ' 21 % Ca 3 (P0 4 ) 2 . Limestone. ( Lower 6 "> 56 ' 41 % Ca 3 (P0 4 ), No. 163. Chas. Thomas estate, 2y 2 miles N. W. of Midway. 11' 11" Clay. 1' 4" Black muck. 2' 2" Sandy phosphate, carries 38.22% Ca 3 (PO 4 ),. 2' Black muck, carries 50.75% Ca :; (PO 4 ) 2 . 1' 8" Fine black muck and sand. Limestone. No. 164. Chas. Thomas estate, y 2 mile S. W. of No. 163. 4' 5" Clay. 1' 9" Phosphate rock, carries 46.37% Ca 3 (Po 4 ),. Limestone. No. 166. Chas. Thomas estate, north of Leestown pike, *4 mile S. W. of No. 165. 11' 2" Clay. 1' 7" Low grade phosphate, carries 32.20% Ca 3 (P0 4 ),. 4' 6" Clay with a few inches of phosphate sand. Limestone. No. 169. On the south side of the highway, between the highway and the L. & N. Railroad, y 2 mile east of Spring Station. 7' 9" Clay. 5' 4" Phosphate rock, carries 43.14% Ca 3 (PO 4 ),. Limestone. No. 170. Estate of Mrs. Harry Wise, just north of house, % mile N. E. of Spring Station. 3' 5" Clay. 2' 5" Containing disseminated phosphate muck, carries 58.12% Ca 3 (P0 4 ) 2 . Limestone. No. 171. Estate of Mrs. Harry Wise, % mile northeast of No. 170. 5' 4" Clay. 4' Phosphate muck, carries 31.37% Ca 3 (PO 4 ) 2 . Limestone. No. 172. Estate of Dr. Samuel A. Blackburn, % mile northeast of Spring Station. 10' 3" Clay. 1' 7" Phosphate rock, carries 38% Ca 3 (PO 4 ) 2 . Limestone. 30 No. 173. South side of Leestown pike, 3 miles northwest of Midway. 10' 4" Overburden. 5' 9" Low grade phosphate muck and clay; lower part con- tains 31.78% Ca 3 (P0 4 ) 2 . Limestone. No. 174. Estate of Mrs. Annie Slack, 2y 2 miles northwest of Midway, south side Lexington pike. 4' 2" Clay. 3' 5" Phosphate rock, upper 2' 8", contains 44.15% Ca 3 (PO 4 ) 2 . Limestone. Frankfort District. No. 175. Estate of Judge E. C. O'Rear, 3y 2 miles east of Frankfort. 5' Clay. 1' 9" Low grade phosphate rock, contains 45.41% Ca 3 (PO 4 ),. Limestone. Note. A hand sample of phosphate chips collected at the gate to the estate of Judge E. C. O'Rear gave 70.65% Ca 3 (PO 4 ),. Several drill holes put down on different parts of the estate were found to contain no phosphate rock. No. 182. Estate of Judge T. H. Painter, 6 miles N. E. of Frankfort, north of South Elkhorn Creek. 2' Clay. 1' 8" Phosphate rock 5 Upper 8 " contained 32 - 42 % Ca 3 (PO 4 ),. Limestone. (Lower V contained 43.67% Ca 3 (P0 4 ) 2 . No. 188. Estate of Judge T. H. Painter, 5% miles east of Frankfkort, just north of the South Fork of Elkhorn Creek. 2' 2" Clay. 2' 7" Phosphate rock, carries 53.98% Ca 3 (PO 4 ) 2 . Limestone. Several drill holes put down on different parts of the estate were found to contain no phosphate rock. iiul'n.,', Forks of Elkhorn District. No. 191. Estate of South Trimble. Scattering fragments of phosphate rock in this drill hole yielded 56.79% Ca 3 (PO 4 ),. A few other drill holes on this estate gave no phosphate rock. No. 192. Estate of George Hannon, 5% miles N. E. of Frankfort, near gate at entrance to estate. 5' 9" Clay. 1' 10" Fine phosphate sand and rock, containing 41.86% Ca 3 (P0 4 ) 2 . Limestone. 31 Lexington District. No. 13. J. B. Haggin estate (Elmendorf) : Quarry on estate, %-% mile east of Maysville pike. 3' Overburden. 2' 6" Phosphate rock, 51.40% Ca :i (PO 4 ) 2 . Limestone. No. 27, 28, 29. Southern Railway (Louisville & Lexington line) near Cahill place, iy 2 miles west of Lexington. 4' Overburden (clay and soil). 3' 6" Massive phosphate rock. 3' 9" Clay. Limestone. No. 27. Top 4' of soil less than 2% Ca 3 (P0 4 ) 2 . This indicates in a general way what may be expected in the top soil of this region. No. 28. Chip from the 3' 6" bed: 53.15% Ca 3 (P0 4 ) a . No. 29. Sample of the 3' 9" bed which may be considered phosphatic clay. 16.44% Ca 3 (PO 4 ) 2 . No. 33. James P. Headley estate, east side Russell Cave pike, just outside Lexington city limits. 8' Overburden (clay and soil). 5' Phosphate rock, 35.14% Ca :1 (PO 4 ),. Limestone. No. 34. Station No. 11, near Hulett's, interurban railway, between Nicholasville and Lexington, Ky. 5' Overburden. 3' Chiefly maganese and iron oxide concretions. Less than 1% Ca a (PO 4 ) 2 . 10' Clay. 5' Massive phosphate rock, upper 4 feet carries 30.98% Ca 3 (PO 4 ) 2 . No. 40. R. W. Higgins quarry, 1V 2 miles northwest of Greendale, Fayette County. 1' Overburden. 3' Phosphate rock, 29.79% Ca 3 (P0 4 ) 2 . Limestone. No. 218. Estate of Judge Jas. H. Mulligan, N. E. of Lexington, between L. & N. R. R. and Russell Cave pike. 5' 10" Clay. 1' 3" Phosphate rock, containing 49.18% Ca 3 (P0 4 ),. Limestone. No. 218A. Estate of Judge Jas. H. Mulligan, W. of No. 218, but E. of railroad. 8' 2" Clay. 4' 3" Phosphate rock, containing 45.06% Ca 3 (PO 4 ) 2 . Limestone. 32 No. 219. Estate of Judge Jas. H. Mulligan, E. of point where Russell Cave pike crosses L. & N. R. R. 4' 3" Clay. 1' 5" Phosphate rock, containing 39.91% Ca : ,(PO 4 ),. Limestone. No. 194. Just east of Mentelle Park, Lexington. (No analysis.) 1' 4" Phosphate sand. Limestone. (Note: Overburden has been scraped away here to obtain clay for brick.) No. 195. 20 feet. E. of No. 194. 5' 3" Clay. 2' Phosphate rock, containing 31.44% Ca ; ,(PO 4 ),. Limestone. No. 193. 25 feet E. of No. 195. 2' 10" Clay. 5' 6" Phosphate rock, containing 30.04% Ca 3 (P0 4 ) 2 . Limestone, overlain by a thin layer of worthless yellow- clay. No. 197. 25 feet E. of No. 196. (No analysis.) 3' 3" Overburden. 4' 11" Phosphate sand and clay. 1' Clay. Limestone. No. 198. Estate of H. G. McDowell, southeast of Lexington on the Richmond pike. 8' 7" Clay. 7' 1" Phosphate rock, lowest 5 ft., carried 48.64% Ca 3 (PO 4 ),. Limestone. No. 199. Estate of J. D. Clark, 3y 2 miles N. W. of Lexington. No phosphate. No. 200 Estate of J. D. Clark, % mile S. E. of No. 199. 4' 4" Clay overburden with some disseminated phosphatic sand near base. 8' 11" Phosphate muck, containing 37.56% Ca :! (PO 4 )v, Limestone. No. 201. Estate of J. D. Clark, % mile N. W. of house. 6' 10" Overburden. 8' 6" Phosphate sand, muck, and some phosphate rock, containing 30.93% Ca 3 (PO 4 ) 2 . Limestone. No. 202. Estate of J. W. Coleman. N. of Lexington, between Newtown and Russell Cave pikes. 4' 7" Clay. 2' 2" Phosphate sand, carries 22.78% Ca :i (PO 4 ),. 2' 3" Barren Clay. Limestone. 33 No 203. Estate of J. W. Coleman, N. of Lexington, between Newtown and Russell Cave pikes. 4' 2" Clay. 2' 8" Phosphate sand and lump rock, carries 49.25% Ca,(P0 4 ) 2 . Limestone. No. 204. Estate of Ernest Erdman, N. of Lexington and E. of New- town pike. (No sample.) 1' 5" Clay. l'-2' 6" A mixture of clay and phosphate rock fragments. Limestone. No. 206. Estate of P. P. Bradley, N. of Lexington and E. of Newtown pike. (No sample.) 1' 3" Clay. 1' 1" Phosphate rock in scattering fragments. 1' 3" Clay. Limestone. No. 207. Estate of P. P. Bradley. 4' Clay. 9" Some phosphate rock. 3' 11" Barren clay. 1' 4" Phosphate rock, containing 45.13% Ca a (POJ 2 . Limestone. No. 208. Estate of P. P. Bradley. 5' 10" Overburden. 4' 8" Phosphate rock, containing 48.51% Ca :i (PO 4 ),. Limestone. No. 211. Estate of Capt. J. D. Yarrington, between Maysville and Russell Cave pikes. 5' 1" Clay. 7" Containing some phosphate rock, containing 45.74% Ca 3 (P0 4 ) 2 . Limestone. No. 212. Estate of Capt. J. D. Yarrington. 6' 10" Clay. 2' Low grade phosphate rock, carrying 20.54% Ca 3 (P0 4 )o. 5' 6" Clay with 1' phosphate rock at base. Limestone. No. 213. Mr. Easton estate, N. E. of Lexington, W. of Maysville pike. 2' Clay. 2' 8" Phosphatic sand, containing less than 5% P 2 O 5 . 2' 2" Clay mixed with a little phosphate. Limestone. No 214. Estate of Judge George B. Kinkead, N. E. of Lexington, just E. of Russell Cave pike. 3' 8" Clay. 4" Fine lump rock, containing 40.79% Ca 3 (P0 4 ) 2 . Limestone. 34 No. 214A. Estate of Judge George B. Kinkead, about 50 feet further south on the hillside from No. 214. 2' 5" Clay. 1' 6" Phosphate rock (no sample). Limestone. No. 214A. Estate of Mrs. Martha Withers, northeast outskirts of Lex- ington. 2' 2" Clay. 2' 1" Containing phosphate in lower 1-2', with 34.11% Ca s (P0 4 ) 2 . Limestone. No. 216. On the Russell Cave Pike, N. 80 W. of Mrs. Martha Withers' estate. 5' 6" Clay. 7" Phosphate rock, no analysis. Limestone. No. 217. Estate of Mrs. Martha Withers, E. side of the estate near Maysville pike. 2' 1" Clay. 1' 4" Phosphate rock. (Note: Struck water in this hole and did not get to bottom. No sample.) No. 217A. Estate of Mrs. Martha Withers, nearer the Maysville pike. 1' 10" Clay. 9" Phosphate rock, carrying 24.31% Ca 3 (PO 4 ) 2 . Limestone. No. 221. Estate of H. Gibson heirs, S. W. of Lexington. 17' 3" Clay. Limestone. (Note: About 15' black muck in the lower part of the hole. Low- est 3-5' contained 21.06% Ca 3 (P0 4 ) 2 . No. 223. A. M. Miller estate, rear of house, South Limestone Street, Lexington. 6' 7" Reddish brown clay. 4' 3" Phosphate sand and clay, 30.93% Ca 3 (PO 4 ) 2 . 7" Clay chiefly, but with some phosphate sand. 2' 4" Barren clay. Limestone. No 224. Estate of A. M. Miller, S. W. of No. 223. 6' 3" Clay. 6' 4" Chiefly clay, with some phosphate sand, no analysis. 1' 2" Phosphate sand. Limestone. No. 226. Kentucky Agricultural Experiment Station grounds. 5' 7" Clay. 7" Disseminated phosphate sand with heavy chert. 4|" Variegated clay and rotten chert. Limestone. (Note: No sample. No phosphate rock.) 35 No. 227. Kentucky Agricultural Experiment Station grounds, % mile S. W. of No. 226 along the road. 6' 1" Clay. 8" Phosphate sand. 4' 4" Low grade phosphate sand and clay. 2' 2" Barren clay. 9" Phosphatic muck and yellow clay, containing 35.10% Ca 3 (P0 4 ) 2 . 1' 8" Yellow drab clay. 2' 9" Clay and heavy chert. Limestone. No. 228. Estate of Joe C. Van Meter, S. of Lexington, and W. of Tates Creek pike. 8' 4" Clay. Limestone. No phosphate rock. No. 229. Estate of Joe C. Van Meter, S. of Lexington and W. of Tates Creek pike. 5' 11" Clay. 8' Iron manganese concretions. Limestone. Two characteristics stand out above all the others in the sections given above, these are the great varia- tion in thickness and composition of the phosphate rock. This is characteristic of the entire brown rock phosphate area. To obtain a better idea of the composition of the different grades of rock it would have been desirable to wash each sample as drilled, thereby separating muck> sand, and lump rock. This is done in practice in prepar- ing the mined rock for market for conversion to acid phosphate. It could not be done by the writer in the field without much inconvenience. Tha analyses of the hand specimens of lump or plate rock throw some light on what might be expected from the lump rock in the sections, and where the specimens were collected and their analyses compared with a few of those of the lump rock itself selected from the drillings, the results show fairly close agreement. LOCALITIES TO BE PROSPECTED. It must not be inferred that all the promising locali- ties in the blue grass region have been examined and prospected, for such is not the case. The co-operative 36 work earned on by the United States and Kentucky Geological Surveys was limited by the available funds, and it is known that prospecting by private parties has been carried on in otjier areas and which without doubt has yielded results which may be as promising or much more so than those obtained in this investigation. In a cut on the Louisville and Nashville Railroad, within the town of Versailles, beyond the iron bridge one-eighth of a mile west of the concrete highway bridge, samples were collected from probably the Woodburn member since colmnwuia halli was observed. Of three samples collected one gave 27.14 per cent., another (No. 25) gave 73.30 per cent., and a third yielded 20.84 per cent, cal- cium phosphate. The selected chips in sample No. 25 indicate what the lump rock may run in this region. South of Versailles, on the west side of the Nicholas- ville pike, on the farm of Ball brothers, chips were noted in abundance on parts of the farm, especially in the rear of a group of small cabins. The samples collected here gave a 79.49 per cent, calcium phosphate. To the northwest of Versailles, where the Midway pike leaves the trolley line, a sample collected near the Fishback place yielded 76.23 per cent, calcium phosphate. Other analyses of selected samples not included in the tables above are given below. It should be remembered that these are selected hand samples of chips which represent lump rock alone and not the run of a drill hole or pit. SELECTED SPECIMENS OF PHOSPHATE CHIPS. Wallace District. Per Cent, of Phosphate of Lime. Ca 3 (P0 4 ),. No. 47 61.53 No. 48 .. 76.12 No. 49 .. 64.03 No. 50 12.37 No. 51 80.67 No. 52 77.47 No. 56 77.64 No. 47. R. S. Stark estate, 1% miles south of Wallace, at side of private roa() and 70 per cent, and but 5 per cent, of the total showed more than 70 per cent. The latter material was for the most part collected from well exposed sections in the old workings of the Central Kentucky Phosphate CYmpany, near Wallace. The remaining 65 per cent, con- tained less than 50 per cent, calcium phosphate, the great buik of the material having from 30 to 50 per cent. The number of drillings made in the other districts was not very large, not large enough to base close esti- mates on. The results obtained are outlined below. In the area between Midway and Spring Station, where prospecting was carried on, about 25 per cent, of the samples obtained in drilling contained between 50 and 60 per cent, calcium phosphate, and about 5 per cent, be- tween 60 and 70 per cent. The remaining 70 per cent, contained less than 50 per cent, calcium phosphate. The great bulk of the material collected from drill- ings in the vicinity of Lexington contained less than 50 44 per cent., wliicli is likewise true for the Forks of Elk- horn district. The reader may reach his own general conclusions from a study of the analyses given above, bearing in mind that all the sections and analyses num- bered 100 and more refer to drill records and the samples obtained from them. In the case of selected specimens from old excavations or natural exposures, the results are given elsewhere. They indicate that the washed lump rock, which is virtually what most of the latter material represents, contains more than 70 per cent, calcium phos- phate in many localities and one sample collected from the Thomas Dunlap farm, 2 1/ -> miles southeast of Wallace, near South Elkhorn Creek, gave 80.67 per cent, calcium phosphate. This high content in bone phosphate does not appear to be wholly unique, for in a table comprising 6 analyses Waggaman* states that hard, brown, heavy plates of phosphate rock collected on the Slack farm, 3 miles northwest of Midway, contained 81.08 per cent, calcium phosphate. Foerstet likewise reports a sample running 82.37 per cent, calcium phosphate from the same farm. It is probable that the two samples were collected from the same pit. Foerste likewise reports a sample from the Lister Wither spoon farm, near the Versailles- Midway pike, which contained 80.80 per cent, calcium phosphate. Thus it appears that while occasional occurrences of lump rock are found containing more than 80 per cent calcium phosphate and although rock in workable quan- tities will be found running up to present commercial re- quirements, that is containing 70 per cent, and more BPL, it is quite safe to affirm that the bulk of Kentucky phos- phate rock will be found to contain less than 70 per cent. BPL. This means that in the most promising areas the reek will have to be carefully washed and cheaply worked by the most modern, labor-saving devices to bring it up to present commercial standards so that it may be able to compare with Tennessee rock. Without doubt much of the Kentucky rock of low or intermediate grade must wait for cheap chemical or electrical processes of con- centration. *Wa,^aman, W. H. A report on the natural phosphate of Tennessee, Kentucky and Arkansas. U. S. Dept. of Agriculture, Bureau of Soils, Bull. 81, p. L'5, 1912. fKentucky Oeol. Survey, Series TV., Vol. I., Pt. I., 1913, pp. 431-439. 45 ORIGIN. SOURCE OF THE PHOSPHATE. The phosphate was de- posited originally on the floor of a shallow sea. Some of it may have been chemically precipitated directly from solution, and some may have come from phosphate se- creting- organisms which flourished in the water of the Ordovician sea. The phosphate probably came from both these sources. Such organisms exist at the present time and some of them have been shown to have shells consisting largely or almost wholly of calcium phosphate. F. AV. Clarke and AY. C. "Wheeler* have shown that the element phosphorus occurs in abundance in the shells of certain brachiopods, crustaceans and alcyonarians. Certain worm tubes are also notably phosphatic- The exact original nature of the phosphates is not known since there is not enough basic material present to have formed the normal tricalcium phosphate. Ultimately it reaches this form in the sediments. Some of the phos- plmtic alcyonarian corals contain from 7.95 to 13.35 per cent, calcium phosphate. Certain of the brachiopods, es- pecially the lingulas and glottidias, are highly phos- phatic, containing from 74.73 to 91.74 per cent, calcium phosphate, and some of the phosphate present is repre- sented as a magnesian salt. The analyses of crustaceans given show a range of 6.57 to 27.44 per cent, calcium phosphate, with an exceptional analysis of a shrimp shell showing 49.46 per cent, calcium phosphate. Some worm tubes show as much as 20.72 per cent, calcium phos- phate. These results are interesting not only quantita- tively, but qualitatively as well. Without doubt even minute quantities of calcium phosphate in the shells of animals have an important geologic and economic signi- ficance since in connection with the formation of all our phosphate deposits and other economic minerals as well, the factors of time and process of mechanical concentra- tion are highly important. Even with only minute quan- tities of calcium phosphate originally present, slow pro- cesses of concentration acting over long periods of time produce important results. ORIGINAL MODE or OCCURRENCE. The original phos- phatic material as now seen in nature, that is the phos- *U. S. Geol. Survey Professional Paper Xo. 102, 1917, p. 50. 46 phatic material as originally deposited, occurs in definite bands in the limestone mixed with calcium carbonate. There is little question that these highly phosphatic bands are original and that they were laid down alter- nately with bands of limestone containing, to be sure, some phosphate, but essentially less phosphatic than the intervening layers. The illustrations taken in the Mt. Pleasant, Tennessee, brown rock field, in the Wallace, and other localities in Kentucky (see Plates VII. and VIII.) illustrate this alternate banding. Typical cross bedding of the phosphate and calcium carbonate layers was also observed at the Wallace workings. The abund- ance of the cyclora casts not infrequently gives the rock an oolitic and almost botryoidal appearance, but the little rounded particles are not necessarily true oolites, and they are usually not. The alternating rich and lean phos- phate layers thicken and thin and pinch out abruptly in a word they have all the characteristics of a normal cross bedded, sedimentary rock deposited where there was some current action. Many samples were collected showing the marked difference in the phosphate content between these alter- nating layers and in a specific case which may be taken for illustration, a sample of the purest phase of the lime- stone in a given ledge yielded less than 1 per cent, cal- cium phosphate, whereas the phosphate lasers inter- bedded with it yielded 72.21 per cent, calcium phosphate. That is, of course, an extreme difference and it is quite likely that all the transitional compositions may be found in these layers, from pure limestone at the one end to the very highest grade phosphate at the other. In the bands or layers which are notably phosphatic, a certain minute fossil a coiled gastropod of the genus cyclora is markedly abundant. In some specimens the casts of the interior of these shells are so numerous as to give hand specimens an oolitic appearance. Whether the shells of these small organisms were originally phosphatic cannot be stated with certainty. The fact that the exterior shells have dissolved and left only casts of the interior tends to indicate that the exterior shells were calcareous. Their abundance and structure rendered them admirable receptacles for the finely di- vided and perhaps almost impalpable calcium phosphate 47 deposited on the floor of the Ordovician sea which hard- ened in the shapes of the interior of the shells in which forms they are now found. The mechanical role which these minute organisms played in the concentration of calcium phosphate was apparently a very important one. Whether the chemical role was of any importance can- not be stated, nor may it ever be known. Clarke and Wheeler's results do not indicate that the gastropod tests which they examined are important carriers of cal- cium phosphate. It may even be true that the occurrence of the phosphate at certain horizons may be due to mechanical concentration effected by the abundance of these coiled gastropods, they having served as natural receptacles for it. Large organisms the brachiopods likewise acted mechanically as receptacles for the finely divided phosphate and the illustration shows the cast of the interior of a brachiopod rafenisquina alternata collected by A. M. Miller near Versailles, Woodford County, Kentucky. The shell itself has been replaced by silica, a portion of which still remains as the white patch in the illustration, (Plate XI.) The cast of the interior has been formed by calcium phosphate which forms the mass of the specimen. THE METHOD OF CONCENTRATION. The evidence re- veals that a great deal of calcareous material was de- posited with the phosphate and that the latter, as it now occurs, is the result of leaching the calcareous parts of the originally phosphatic limestone. Some of the phos- phate as now observed may have been originally quite rich and some of the leaching may have occurred while the deposits were yet exposed to current action on the ocean floor. This, however, is pure speculation. It is known that as a result of subaerial leaching the dissem- inated phosphate has been concentrated as the calcar- eous parts have dissolved away, and there has resulted a fjur grade phosphate deposit from what was a low grade material. In other wonls, the brown phosphate rock deposit of Kentucky, as it occurs today, rer^e^ents a clear case of secondary concentration or enrichment. Several factors have played parts in the leaching or dissolving of the calcium carbonate deposited with the phosphate. It is presumed that the solution took place by conversion of the normally insoluble lime carbonate 48 to the soluble bicarbonate according to the chemical re- action. H 2 C0 3 +CaC0 3 =CaH 2 (C0 3 ) 2 . The carbon diox- ide was furnished by percolating- meteoric waters. Thus the first factor is a position near enough to the surface to be brought into contact with surface waters. In describing the stratigraphy of the phosphate area, the Brannon member was stated to underlie the richest phosphate horizon in central Kentucky. It was there described as a firm, hard limestone, a good water bearer with its outcrop marked by springs. It is the limestone occurring in the numerous sinks of this region. The overlying member, the Woodburn, which carries the phosphate principally, is granular, thin bedded, and likewise contains sinks. In other words it is of a char- acter to readily weather and dissolve away. This com- bination of an underlying more or less impervious stratum and an overlying granular limestone is an ad- vantageous one for the rapid accumulation of phosphate and no doubt was an important factor in the segregation of the phosphate deposits. Thus the character of the associated sediments may be considered the second im- portant factor in the rapidity with which the phosphate rock may concentrate. Two other factors have helped the leaching process, namely, the laminated character of the limestones and associated phosphate layers already referred to, ^ and the joint planes which are characteristic of these lime- stones, as they are of most rocks. The leaching of the calcareous portions begins along the joint planes between the laminae, especially along those planes between the limestone and the phosphate bands, which afford easy means of attack. As the leaching progresses the solu- tion cavities along the joint pianos grow wider and deeper and ultimate in the "cutters" which have been already described. The undissolved masses of limestone remaining between the cutters are called " horses." The cutters have, as would be expected from the theory ascribed for their formation, very definite courses too great a regularity to admit that their formation has been largely fortuitous. In the vicinity of Wallace the courses of the cutters were between north 8 west and north 25 west. In Mt. Pleasant, Tennessee, where much better opportunities exist to observe this phase of phos- 49 ]>liate occurrence, the trends of the cutters follow quite definite directions also. The limestones not only are leached from above and on the sides of the horses (cutters), but solution takes place laterally, or along' the limestone and phosphate laminae, so that actual projecting ledges or umbrella rr.eks form on the sides of the horses. Sometimes leach- in tv proceeds to the point where limestone masses actual- ly become completely detached through solution and lie amid the deposits of the phosphate rock. The irregularities of the underlying rock surface and the manner in which the phosphate settles down on it, has given rise to the undulations which occur in the phosphate rock deposits. These phenomena are well bi ought out in the illustrations. The intervening clay layers associated with the phosphate rock represent the original beds of non-phosphatic clay bearing limestone. This material weathers to a product commonly referred to as muck. Disseminated phosphate sand is associated with plate, lump or hard rock and with the muck. Most of this disseminated sand without doubt represents orig- inally disseminated phosphate rock scattered throughout the (deposits and which has become concentrated through the leaching of the limestone. Most of the sand is sim- ply Cyclora casts composed of phosphate, again illustrat- ing the important mechanical role played by these minute organisms in the concentration of this valuable ferti- lizer. The term sand is not a good one from the view point of origin, for though most of the little fragments are rounded as fragments of such casts would be ex- pected to be, the rounded shapes are not due to mechani- cal attrition, but are original. Some very interesting observations on Kentucky rock have been made by Arthur M. Miller.* Miller be- lieves in an original segregation of the phosphate de- posits, that is, a segregation at the time they formed on the ocean floor. He says, "this original segregation of the phosphate has in no case, however, given deposits rich enough to be commercially valuable. The latter de- posits have resulted from the weathering of the deposits of the first concentration. Though concentrated as the >Ky. Geol. Survey, Series IV., Vol. I., Pt. I., 1913, pp. 327-328. 50 result of weathering, we do not believe that the facts of occurrence warrant the explanation that in weathering the 'carbonate of calcium has been dissolved out leaving the phosphate of lime behind' that in other words it is simply a residual deposit due to the leaching out of a more soluble constituent. "Were the latter the case it should be possible to find many instances of deposits of unleached phos- phate where the amount of phosphate in the same volume of deposit equals that which we do now find in the weathered commercial deposits. The same amount of phosphate should be there plus the original amount of carbonate of lime 1 ; but in no instance is this the case. On the contrary, all the facts point to an actual con- centration of the phosphate into less volume as the re- sult of a process of replacement. "We have here the same phenomenon as is illustrated by certain iron ore de- posits. Water with iron in solution is checked in its downward descent by meeting relatively impervious stratum. Vnder these conditions the saturated stratum (commonly a limestone) immediately above the relative- ly impervious stratum is altered by replacement; iron replaces calcium, the latter being finally carried away in the form of bicarbonate by the water. "So in the case of concentrated phosphate of lime deposits: insoluble tricalcium phosphate acted upon by organic acids in the superficial layers of rock waste has its phosphorus rendered soluble ('available'). Entering into solution in the form of phosphoric acid, it passes downward to the lower 'rottenstone' and bed rock layers. Here the phosphorus 'reverts' to its original tricalcium phosphate condition, replacing the non-phosphatic or relatively non-phosphatic limestone. "The final theoretical reaction is expressed by the following equation: Ca. H 4 (POJ.,+2 Ca. CO,=(PO 4 ) 2 + 2H,O+2C(),." This theory of the formation of Kentucky phosphate rests on the solubility of calcium phosphate. Without any doubt this compound in its natural state is sumcient- ly soluble to bring about important accumulations over long periods of time, due to replacement, and possibly replacement has been an important factor. As pointed out above, in practically unaltered specimens of the phos- 51 pliatic layers interbedded with limestone, the rich phos- phatic layers are present. These were collected by the writer and analyses made in the survey laboratories showed more than 70 per cent, in calcium phosphate. Foerste* also reports mi weathered limestone near Ver- sailles from the Woodburn member carrying 55.5 per cent, calcium phosphate, overlain by rock containing only 9.39 per cent, of the same ingredient. Thus to the writer the idea of replacement is not an absolutely nec- essary factor in accounting for the concentration of the phosphate rock. He is willing to admit that replacement may have played a part, but feels that the explanation that has been given, and by which other writers have explained the formation of the Tennessee phosphate de- posits, will apply to the Kentucky field. THE BROWN PHOSPHATE ROCK INDUSTRY. GENERAL CONDITIONS. The Kentucky phosphate field is practically a virgin field. From its study and a comparison of it with the Tennessee field, the writer feels that local conditions are similar and the problem of working the Kentucky de- posits must be along much the same lines as in Tennes- see. For this reason it is thought that a brief descrip- tion of the mining methods employed in the Mt. Pleasant, Tennessee, field will prove of interest here. There has been going on for some time in the Mt. Pleasant phosphate field and without doubt in other parts of the Tennessee brown rock phosphate areas, a change that will result in leaving very little or no wasted phosphate rock in the ground. Some phosphate is going into the waste ponds, but the time will without doubt come when all this material will be reworked, and even now some companies are working or planning to work these old tailings. Modern mining and milling methods of the last decade have revolutionized the brown rock phosphate industry, and incidentally are conserving this valuable fertilizer material. They are in striking con- trast with the crude and wasteful methods formerly em- ployed. When phosphate was first mined in Tennessee it is safe to say that at least half of the good material such, for example, as is now being worked was thrown *Loc. Cit., p. 381. 52 away. A great deal of this cannot in the nature of things be recovered, for in the course of time it has become so thoroughly mixed with clay and in places so covered with overburden as to make its recovery at a profit im- possible. The lessons learned in Tennessee no doubt will be of value in working the brown phosphate deposits in central Kentucky. The object, of course, in preparing phosphate for market is to remove as much of the clay, chert, and limestone as possible from it. It is not possible to re- move all these impurities, especially in the case of clay and sand. There is no sharp division between the finest phosphate sand and clay and it would obviously be wasteful to carry the process of obtaining fine phosphate sand beyond the point where the cost would offset the value of the phosphate obtained. This is one of the prac- tical considerations connected with the modern conserva- tion of phosphate rock which perhaps has not always been given just and deserved consideration. These prac- tical difficulties have resulted in the loss of much fine phos- phate along with the silica sand and clay. Owing to the similarity of finely divided phosphate and silica sand in specific gravity, no mechanical process has been de- veloped to effect a further saving. As the problem now stands the general development of some concentration process is required to effect a further recovery of low grade phosphate both in Tennessee and Florida, where the consumers are demanding a high grade product. The point beyond which it is not practicable to carry preparatory treatment is not fixed and standards vary from time to time and probably at a given time among individuals or corporations. Thus in the phosphate min- ing industry as practiced in Tennessee in the early nine- ties, rock was discarded which has a high value today, and the former apparent lapses from the highest stand- ards have in the course of time proven to be not lapses at all, but simply necessities imposed by trade conditions of the time. In other words the phosphate once discard- ed is now being used. The open cut or surface methods of mining brown rock as practiced in the Tennessee field, and which will be the methods employed in the Ken- tucky field, are peculiar in this respect and the gen- 53 eralizatious made do not cover many other classes of mining- and certainly will not apply to underground min- ing- in general. GRADES OF COMMEIKTAL IJKOWX PHOSPHATE ROCK. Most of the brown phosphate rock from the Mt. Pleasant, Tennessee, field is shipped in three grades, namely, those containing 72, 75, and 78 per cent, of cal- cium phosphate. The percentage of iron and aluminum oxides ("I and A") remaining in the washed product has an important hearing on the value of the rock. The usual guarantees are given below. .For each per cent, in excess of the guaranty, '2 per cent, of calcium phos- phate. (BPL) is deducted'. Table of Guarantees C-howir.g the Relation Between Phosphate: and ii on rnci Alurrunn CcnLeni. Fe_O. ; +Al,O :; BPL T and A Per cent. Per cent. 70 6.5 72 5.5 75 5.0 76 4.1 78 to 80 4.0 Five to five and a half per cent, iron oxide and alumina is the usual maximum allowed and that is usual- ly referred to as "I and A" in the trade and in com- mercial analyses. At one time only rock of 78 per cent. grade was shipped from the Mt. Pleasant field and rock of this grade is still known as ' ( export rock. ' ' The guar- anteed content in phosphate of lime, "bone phosphate" or "BPL" as it is commonly referred to in the trade, next fell to 75 per cent., and at the present time many of the companies are finding it difficult to ship this grade exclusively, and the life of the 75 per cent, rock is limited. Every per cent, of iron oxide and alumina less than the 5 per cent., is regarded as equivalent to an additional 2 per cent, of calcium phosphate, for it is considered that in the subsequent treatment of the phosphate in the man- ufacture of fertilizers the harmful effect of 1 per cent, of iron oxide and alumina offsets the good effect of 2 per cent, of calcium phosphate. If much more than 5 per 54 cent, of iron oxide and alumina are present the superphos- phate tends to become gummy and farmers find it difficult to drill it into the land. A few samples of Kentucky phosphate rock were se- lected for analysis for their content in iron, alumina, and fluorine, in addition to their content in phosphate of lime. The results of these analyses are given below. The content in iron and alumina shown are too high to come within the normal commercial requirements of the pres- ent time and indicate, as pointed out in other places in this paper, that the bulk of the Kentucky phosphate rock will no doubt have to wait for the general introduction of cheap chemical or other processes of concentration be- fore it is able to compete with the high grade phosphate rock from the other eastern states. Analyses of Kentucky Phosphate Rock. (W. C. Wheeler and R. M. Kamm, Analysts.) Ca 3 (PO 4 ), ALO 3 Fe,O : ; F. No. 108B 63.87 5.29 2.09 1.38 No. 112A 60.87 4.35 3.50 1.02 No. 120 28.92 7.46 5.29 0.70 No. 126B 54.25 4.63 1.42 1.18 No. 133 24.56 10.66 6.62 0.85 No. 141 35.21 5.21 5.29 0.92 No. 143 37.56 2.50 6.05 0.95 No. 108B. Mrs. M. Murray farm, 1% miles southeast of Wallace, and north of Frankfort and Lexington pike. No. 112A. Henry L. Martin estate, % mile east of Wallace, and north of Frankfort-Lexington pike. No. 120. H. L. Martin, Jr. estate, l 1 /^ miles southeast of Midway. No. 126B. James J. Nugent, in orchard just northeast of Wallace crossroads. No. 133. E. L. Lillard estate, 2y s miles southeast of Midway, near South Elkhorn Creek. No. 141. E. L. Davis estate, along the Louisville and Nashville Railroad in small sink, 1% miles northwest of Midway. No. 143. Mrs. Charles Nuckols estate, 1% miles northwest of Midway. PREPARATION OF PHOSPHATE ROCK FOR MARKET. There are many stages to be considered under the head of preparation of phosphate rock for market, but they may all be subdivided into 3 major operations as 55 follows: (1) removal of overburden; (2) mining; and (3) milling, in which is included drying. The present methods of utilizing and thus preserving from loss the brown phosphate rock supplies, especially in the Mt. Pleasant field, are included under the above headings and therefore will be described in connection with them insofar as this can be done. REMOVAL OP OVERBURDEN. The overburden of the brown rock phosphate de- posits in the Mt. Pleasant, Tennessee, field varies from one foot upwards. Usually it is less than 20 feet, but a thickness of 30 feet is known but is excessive in those places where mining has been in progress. The methods of removal of overburden are diverse. Under exceptional conditions the old time crude and expensive hand methods have to be resorted to, but in most places, es- pecially where virgin ground is being opened up and where conditions are comparable with what may be expected in Kentucky, operations are conducted in the most up-to-date fashion, as the illustrations (Plates XII. to XVI.) show. Where the overburden is not very thick or hard it may be simply pried up and removed with scrapers (Plate XII. ), or it may be loosened with dynamite and then removed with scrapers. A favorite method of getting rid of the overburden, used especially in ground that is being reworked, is to first "hog" or undercut it, pry it off with bars, and then scrape or carry it away. The drag line excavator (Plate XIV.) and the steam shovel (Plate XV.) are types of up-to- date machinery used to remove overburden in the Ten- nessee field. The hydraulic method (Plate XVI.) is also used and this would do well in the vicinity of Elk- horn Creek, Kentucky. Both the overburden and the rock beds are removed by this last named method, which is simplicity itself in action and which requires a mini- mum of labor in operation, namely one man to handle the hydraulic gun and two to keep the sluices clear. Of course this last named method can only be used where there is an abundant water supply. Occasionally narrow benches are stripped by hand methods. The dirt is more or less undermined by the re- moval of the underlying rock and the bank caved over 56 into the previously mined outbench by prying with under rods from above. In the case of deposits stripped by scraper outfits, (Plate XII.) the outfits are such as are used in ordinary railroad work and consist usually of ordinary and five wheeled scrapers with a hook team extra and a plow team. This work is usually contracted at 141/2 cents per cubic yard. The major portion of the stripping is now done by class 14 Bucyrus Drag Line Excavators mounting a 70-foot boom with a iy 2 yard bucket. (Plate XIV.) This machine is adapted to the removal of overburden that does not average more than 15 feet in thickness. With more than this depth the pits become too narrow at the bottom. In Hickman County, Tennessee, where the over- burden averages 30 feet, a class 24 drag line machine has been used. This has a 100-foot boom and a 3V> yard bucket. In general it cannot be said that the workability of a bed is regulated by the depth of overburden. There are other factors entering into the problem. If the phos- phate bed is a very thick one, the overburden may be quite thick and still may be removed and the operation be a profitable one. On the other hand, if the bed is very thin but exceedingly high grade, it may still pay to remove what appears to be an excessively thick over- burden. COSTS OF REMOVAL OF OVERBURDEN. The cost of operating the class 14 machines is as follows : Cost of Operating Class 14 Bucyrus Drag Line Excavator. Per Shirt. 1 runner ($150 per month) $6.00 1 fireman 2.50 1 teamster 1.75 1 ground man 1.50 1 foreman 3.00 1 team (owned by company) 3.00 Coal, 2 tons at $2.40 4.80 Cable wear 5.00 Repairs, oil, and supplies 3.00 6% interest on $13,000; 250 shifts 3.20 10% depreciation .. 5.20 $38.95 57 The above items of expense are for a machine hav- ing caterpillar traction for moving. If a timber and roller machine is used an extra ground man is required. The capacity averages 1,000 cubic yards per 10-hour shift, though often .1,300 to 1,400 yards are dug under favorable conditions. While the larger size machines average more in yardage, the operating costs also in- crease so that the cost per yard is nearly the same. In those mines where hydraulic stripping is used owing to the excessive depth of overburden, or where mining conditions require it, the cost of removal amounts to about 7 cents per cubic yard. At two mines in Tennes- see where this method is employed the bank is cut down by a hydraulic monitor, using a 2 o.r 2~\t> inch tip. The water pressure usually needed is 150 to 175 pounds per square inch. The water flows back from the face carry- ing from 10 to 20 per cent, solids into a pump well.. From the sum}) the Avater and overburden are pumped to the waste ponds by an 8-inch direct connected motor driven centrifugal pump. The pump requires from 1,500 to 2,000 gallons of water per minute for full capacity with a 75 horse power motor. METHODS OF MINING. Much of the mining in the Mt. Pleasant, Tennessee, field has been done by hand on account of the method of occurrence of the brown rock. The steam shovel has not proved successful because it is unable to discrim- inate between the grades of ore mined, with the result that much clay and flint get into the product and has to be removed subsequently. The cantilever adjunct to mining which is employed at one mine in the Mt. Pleas- ant, Tennessee, field is unique. The hydraulic method of mining is used at two plants and has many advantages as pointed out under the preceding topic. These me- chanical, methods of mining and removing overburden which have cheapened operating costs, have played the major part in conserving Tennessee brown phosphate rock and without doubt will be the means whereby Ken- tucky rock may hope to take its place on the market. As hydraulicking is practiced in Tennessee, the limestone horses often get in the way and have to be blasted out. But this is not difficult, owing to the loose or platy character of the phosphatic limestone associated 58 with the brown rock deposits. In addition to the hy- draulic method which may be employed only in certain favorable locations, hand mining is also employed, es- pecially where the ground is being reworked. Where hand mining is practiced the ore is usually screened on the spot where the miner is at work. The fine material passes through the screen and is saved and washed, and the coarse rock which is left is hauled away and dried by burning on ricks of wood in the open (see Plate XVII), thus saving rehandling in the mill. The lump rock, as mined, usually contains from 20 to 21 per cent of moisture and drying it in this way reduces the moisture to 1 per cent, or less. In certain places where mining with the hydraulic giant is not practicable or where the giant fails to get all the rock, hand mining has to be resorted to. WORKING CUTTERS. The term "cutters" has been explained and the fact that the phosphate rock in them was left unmined in the early days of brown rock mining has been pointed out. The development of cutters, which took place along orig- inal joint plains, varies greatly within the restricted Mt. Pleasant field and may be expected to vary much in the Kentucky field. In some places in Tennessee they are of large size and some were observed 30 to 35 feet wide and as much as 20 to 25 feet deep (Plate XVIII.), averag- ing probably 18 to 20 feet. In these abnormally wide and deep cutters, it is not uncommon to have small lime- stone horses. Some of the cutters, on the other hand, are so narrow that the phosphate rock in them can be removed only with difficulty. (Plate XIX.) Hand methods of mining have to be employed almost exclusively to remove phosphate rock from these cutters owing to the peculiar method of its occurrence. (Plates XVIII. and XIX.) Hydraulic methods have been employ- ed in places. Owing to the depth of the cutters the work has been done in benches of convenient height for the miners, (Plate XVIII.) The ore is picked out and shoveled from bench to bench and finally into wagons, in which it is hauled to the mills. Mining the deep cutters is usually carried on in fair weather and when the roads are good. In working over virgin ground at the present time the rock in the cutters is readily and cheaply obtained by 59 the cantilever method. (Plate XIII.) The material from the shallow cutters is picked out and screened on the tines of a phosphate fork or on a small, movable, 1-inch mesh screen. The coarse rock is dried or burned on ricks of wood (Plate XVII.), and the muck is taken to the mill where it is washed. The old cutters containing phos- phate rock are located by hand prospecting with a long- sharp steel rod. THE COST OF MINING PHOSPHATE ROCK. The cost of mining phosphate rock depends on sev- eral factors, chief among which is the depth and expense connected with the removal of the overburden. It will be of interest to note here average costs in the most im- portant phosphate producing states. In South Carolina during the past ten years, as much as 22 feet of over- burden have been profitably removed and river rock has been dredged from a depth of 52 feet, including a cover of 16 feet of sand and muck. In Florida, where a higher grade rock is produced, it is profitable to mine rock hav- ing an overburden of greater depth than 20 feet the average maximum in South Carolina. According to data furnished by various companies to the Federal Trade Commission* the cost of mining Florida land pebble, in- cluding washing, drying, etc., ranges from about $1.65 to $2.50 per gross ton, not including amortization of in- vestment or royalties in case the mining is done on that basis. The cost of mining Tennessee brown rock ranges from about $2.75 to $3.14 per gross ton and these are the figures of greatest interest in connection with the Kentucky field. The cost of mining rock in South Caro- lina is considerably higher. The following figures were taken from the average costs of a Tennessee mine during six months of good mining weather :f Per ton cents. Mining $0.64 Transportation and team expense 0.23 Washing 0.46 Drying 0.47 Shipping and track expense 0.09 Total per long ton of dry rock $1.89 *Rept. on the fertilizer industry, 1916, p. 101. fBarr, James A. Tenn. Phosphate Products. Bull. No. 93, Am. Inst. Min. Engrs., Sept., 1914, p. 2410. 60 The work of mining- is chiefly done by contract, the price being 25 cents per tram when one handling only is required. Where two casts are required 35 to 40 cents per tram is paid. The miners keep the track up to the mining face. WASHING AND DRYING. The washing processes whereby the mined brown phosphate rock is treed from clay, chert, and limestone are elaborate and the mills in which the work is done are for the most part large and modern. These modern wash- ing plants which have done so much to make the mining of low grade brown rock profitable, and which, therefore, are playing such an important role in the conservation of this class of phosphate rock, have practically all been installed during the past 10 or 15 years. The principles of the washing process are identical throughout but the details of manipulation differ at different plants. The phosphate rock as mined is brought to the washer either in wagons or by tram. Where hydraulic mining is prac- ticed it goes to the plant through a flume. The material mixed with water is delivered into a hopper at the top of the mill and the subsequent operations for the most part are conducted by gravity. From the hopper the rock passes through a toothed revolving crusher and then into log washers. From the washers it passes to a cylindrical or conical screen with circular perforations. The coarse or lump rock which fails to pass through the screen passes on to a picking belt where limestone and chert fragments and clay balls are removed. The ma- terial then goes to the wet storage sheds or piles to be later dried. The fine material may go through a settler or clarifier provided with riffles, or through several set- tling tanks in succession in which the sand settles out. The clay and sand not caught in the process goes to the waste ponds. The above description briefly outlines the fundamentals of the washing process as carried out at most of the' plants handling brown rock phosphate in the Mt. Pleasant, Tennessee, field, but, of course, as has been mentioned, details are widely divergent. The clay and the phosphate sand which pass to the waste ponds are of great interest in the problem of conservation. When the material reaches the waste pond 61 the coarse sand settles out first and naturally nearest the_ end of the waste pipe or flume. This material is the highest in calcium prosphate. It is planned to work ma- terial of this character at one of the plants near Mt. Pleasant, and already at another the old tailing dumps are being worked. At this plant much attention has been paid to the process of separating the clay and phosphate sand. There is a washer at this particlar plant which differs from any other in this field and is most throuogh in its action. The clay resulting from the action of this washer was observed in the waste pond. It has been in suspension for a long time and material taken and nibbed between the fingers appeared of almost impalpa- ble fineness. Some of the phosphate sand from this wash- ing process is so fine in texture that it sifts through the meshes of the sacks in which it is shipped. It has been suggested that material from such waste 1 ponds might be used in its present form on farm lands, but this lias been found impracticable as it will not bear the cost of transportation, but the high phosphate content in cer- tain of the samples collected from such waste ponds is noteworthy. Drying is accomplished in two very different ways which arc representative of the old and new methods employed in the Tennessee brown phosphate 1 field. At nearly all the large plants modern rotating' cylindrical dryers, similar to rotary cement kilns, are in use, but the rock is fed both at the hot and cold ends. It would seem that the latter method would be the more efficient. There is generally some special cause when the old fashioned method of drying 1 on wood ricks is employed and where it is in use it generally saves extra additional handling or haulage. Drying* generally reduces the moisture present from 20 or 21 per cent to 1 or 2 per cent. CONSERVATION OF FINES. In drying 1 phosphate rock large quantities of ma- teiial in finely divided form is lost by being carried out of the fiue, owing to the powerful drafts employed, es- pecially in the modern types of dryers. At many of the plants steps have been taken to save this material. This is accomplished by means of bends in the flue, or by 62 hoods or baffles. The analysis of the fine material caught and saved at some of the plants indicates that it is well worth saving. THE PHOSPHATE INDTSTKV AT WALLACE, KENTUCKY. The phosphate deposits on certain farms near Wallace at the time of the writer's visit were under lease by the Central Kentucky Phosphate Company. Since then (June, 1915) they have changed hands and are now being worked by the United Phosphate 1 and Chemical Company which, it is understood, is a subsidiary of the Charleston, South Carolina, Mining and Manufacturing Company. Since work started at Wallace some few years ago it has been carried on intermittently and there have been many shut downs lasting for short or long periods. The total tonnage removed from the Wallace workings has been small and in all has not amounted to more than a few thousand tons (1,500 to 2,000 tons). Since the writer visited the plant in June, 1915, it has been added to con- siderably, and it is expected to resume operations on a larger scale than ever early in 1917. In the early part of this year, the Hawkins farm, which adjoins that on which the old workings are located, has been acquired and it is planned to work out to the Steele and Murray farms which are nearby and under lease. The overburden at the Wallace workings varies from a fraction of a foot to 5 or 6 feet in thickness. It occasionally reaches 10 feet. Due to its thinness, it may be removed directly by scrapers, after it is first plowed up or loosened with pick and shovel. After the removel of the overburden, the phosphate rock is usually removed with pick and shovel, loaded by hand en to wagons, and hauled to the mill. The deposit at Wallace normally ranges from 3 to 5 feet in thickness. The extremes of thickness are 1 foot and 10 feet. When the ore is of the maximum thickness it proved too costly to remove it all according to the methods employed in this field. Electric power is used at the mill. The ore at the mill is shoveled on to a belt which feeds it to a revolving cylindrical dryer 40 feet long and 5 feet in diameter. This is fed with coal which is burned under a forced 63 draft. The ore in the dryer travels forward and down- ward to the hotter end. From the dryer it falls into a pit through which passes an endless bucket conveyor, which carries it to .a horizontal screen conveyor. The latter in turn transfers it to a hopper through which it falls on to burrs or grinders. Before falling on to the burrs, the lump rock is screened, only those fragments which are % inch or less in diameter going into the crushers. The screen is a cylindrical affair containing V-2 inch holes. All the lump rock passes over the screen to a conveyor and goes to a loading bin to be wheeled on to cars later, or it may be clmted directly on to cars. The material which has passed through the crushers is further ground to phosphate flour and conveyed by elevators to its own bin. The ground rock is bagged in paper bags of 100 or 200 pounds each, and shipped in this form for direct application to the soil. The old company whose methods are described above has a spur built to its plant from a short branch line of the Southern Railway running between Georgetown and Versailles, Kentucky. The new company proposes to grade tracks to those farms it proposes to work. TRANSPORTATION FACILITIES. The Wallace area and the area to the west of Mid- way are admirably located with respect to railroad trans- portation. The main line of the Louisville and Nashville Railway between Lexington and Louisville, passes through Midway and the phosphate area to the west be- tween Midway and Spring Station. A branch of the Southern Railway between Versailles and Georgetown passes through the heart of the Wallace area, and the topography or lay of the land about Wallace is such that spur tracks may be built where needed at a minimum of expense. The railroad requirements, therefore, could hardly be improved upon. The Kentucky deposits are also well located from the viewpoint of distribution to the north in Ohio, and northwest in Indiana and Illinois, where more and more raw ground rock is coming into use. The freight rates from Midway to Louisville, Cincinnati, and Cleveland are in each case less than from Mt. Pleasant, Wales Sta- tion, and Nashville, Tennessee, and this difference in 64 freight rates may compensate for a lesser content in calcium phosphate in the Kentucky rock, and where com- position and other conditions are equal, result in a de- mand for the latter. The following table is of interest in this connection: Freight Rates From Mines in Kentucky and Tennessee to Important Near By Markets. Destination. Location of Mines. Freight Rates. [Midway, Ky. .. $1.60 Cincinnati, Ohio Mount Peasant, Tenn. .. 2.50 Wales Station, Tenn. .. 2.50 [Nashville, Tenn 1.80 fMidway, Ky 1.60 Louisville, Ky.... . J Mount Pleasant > Tenn 2.25 A Wales Station, Tenn 2.25 Nashville, Tenn. 1.55 \_ fMidway, Ky 3.22 I Mount Pleasant, Tenn 3.80 Cleveland, Ohio J TTT . Wales Station, Tenn 3.80 Nashville, Tenn. . 3.12 RAW ROCK PHOSPHATE. Finely ground rock phosphate, sometimes called "floats," is used to a considerable extent by farmers, particularly in the middle west, as a source of phos- phorus. It is often lower in phosphate of lime and con- sequently higher in iron and alumina than rock used for acidulating purposes. In the raw condition, the iron and alumina, if in the form of phosphate, are advan- tageous according to certain scientists who have ex- perimented with these phosphates, because they have been found to supply a favorable medium for the germination of seeds. Floats are applied directly in turning under crops, or are mixed with barnyard manure on the theory that the phosphoric acid is liberated and rendered avail- able by the action of the weak organic acids generated during the decomposition of the manure. The future of the Kentucky phosphate field as a source of raw ground rock ought to be good. The use 65 of this material in the states to the north and west is becoming increasingly popular. The advantages in freight i ates as compared with the nearest competing field in similar rock, the quality and other factors being equal, is important, as is also the additional fact that a high content in iron and alumina in the raw rock is not considered sncli a drawback as in rock which is acidulated in making acid phosphate for mixed fertil- izers. Floats have been shipped in the past from the Kentucky field when operations have been in progress in that locality. PIIOSPHATir LIMESTONE AS A SOTKCE OF PHOSPHATE. Directly below the phosphate rock horizon occurs the phosphatic limestone from which the brown rock itself has been derived. This is often platy in structure, the plates of highly phosphatic material alternating with the nearly pure calcareous layers. This platy or laminated structure is original and throws light on the occurrences of the brown rock itself which also occurs in plates separated by layers of muck, clay, and sand, the former corresponding to original layers of phos- phatic limestone, and the latter to the intermediate clay and less phosphatic limestone layers. There must be an enormous tonnage of this phosphatic limestone scattered throughout the phosphatic rock area of the blue grass region of Kentucky. A long period of time must elapse before any attention will be given to this comparatively low grade material as a source of phosphate, but it would be hazardous to say that this will never be done. Analyses of these limestones, some of which are in a leached and some in a partially leached condition, oc- curring in horses between cutters contained as much as 70 per cent, calcium phosphate, and Foerste reports unaltered phosphatic limestone in the Woodburn mem- ber at Versailles containing 55.5 per cent, calcium phos- phate.* In Tennessee some of this phosphatic limestone whose analyses the writer is acquainted with averages more than 42 per cent, in calcium phosphate. The car- bonate and the phosphate of calcium mixture in this material has considerable value as a fertilizer when ap- *Kv. Geol. Survey, Series IV., Vol. I, Part I, 1913, p. 386. 66 plied directly to the land in finely pulverized form, and although it is difficult to predict how or when such ma- terial will be utilized, it seems fairly certain that it will prove of value at some future time. THE FUTURE OF LOW OR INTERMEDIATE GRADE PHOSPHATE ROCK. GENERAL REMARKS. There is associated with all phosphate rock deposits considerable rock which is not up to present commercial requirements in content of calcium phosphate. There is also being produced in connection with the prepara- tion of commercial phosphate rock for market a great deal of low grade material. To bring these classes of material up to commercial grade, that is to a grade con- taining 70 per cent, or more calcium phosphate, various chemical methods have been used. The time will un- doubtedly come when these chemical methods will find much more extended application than at present, and when this time arrives it will result in the utilization of a great deal of phosphate rock now consigned to waste ponds and dumps, and also much which will not bear the present cost of mining. Such methods are of more than ordinary interest in connection with the Kentucky field. The large quantities of by-product sulphuric acid which will become available in increasing quantity as time goes on as the result of the elimination of the smelter smoke nuisance, is an important element in the situation. Im- mense quantities of such acid has in the past been avail- able in southeastern Tennessee, and is potentially avail- able at the smelters in the vicinity of our western phos- phate field. Indeed the chemical method of concentrating phosphate and thus enabling it to be transported long distances may well be worked out in connection with the high grade rock that the western phosphate field is able to produce, and it will also be the means of conserving the enormous quantity of low grade phosphate rock in the Kentucky and other eastern fields. 67 CHEMISTRY OF PROCESS. Phosphate rock is marketed now as such, and in the form of acid phosphate, including in the latter term ordinary super and donble-acid phosphate, the latter con- taining two to three times as much soluble phosphoric acid as ordinary super-phosphate. Before the discovery of the extensive high grade deposits of phosphate rock in this country aiul abroad, the manufacture of the concentrated grades of soluble phosphate was in fairly common practice. The large supplies of high grade phosphate rock have rendered this unnecessary, though in Europe and in parts of the United States this practice is reported to be still in use. The basic reaction involved in the preparation of soluble acid phosphate takes place when ordinary rock phosphate Oa,(P() 4 ), is treated with sulphuric acid. In simple form, the reaction that takes place may be represented thus : (1) Ca,(P0 4 ),+3H,$0 4 =2H,P0 4 +3CaS0 4 . (2) 4H :5 P0 4 +Ca,(P0 4 )^3CaH 4 (P0 4 ) 2 . Eeduced to one equation, this is as follows : Ca 3 (P0 4 ) 2 +2H 2 S0 4 =CaH 4 (P0 4 ) 2 +2CaS0 4 . In the presence of water, which has been omitted from the above equations in order to simplify them, the calcium sulphate would be changed into gypsum by ab- stracting water from the mass. The last reaction is the one desired by the manufacturers. To utilize low grade rock and tailings, and to make concentrated phosphatic fertilizers, the phosphoric acid produced by the first reaction is evaporated in pans until it contains about 45 per cent, phosphoric anhydride. It is then treated with a fresh supply of phosphate rock, when the following reaction ensues: Ca 3 (P0 4 ) 2 +4H,PO 4 =3CaH 4 (P0 4 ) 2 . It will be observed, therefore, that ordinary super- phosphate is largely a mixture of soluble calcium phos- phate and gypsum, while the double acid phosphate con- tains little or no calcium sulphate, or dehydrater, and thus has to be artificially dried. Either the phosphoric acid itself, the double phosphate, or such compounds as potassium or ammonium phosphate, might be shipped from our western field, since they are highly concen- trated products. 68 EXPERIMENTAL WORK IN THE WEST. CHEMICAL METHODS. With reference to the results accomplished to date in the west toward the production of a high grade phos- phate product which may be shipped to eastern markets, the following is of interest:* The first effort, having in view the production of a high grade phosphate product which would stand the cost of shipment to eastern markets, was instituted by the Mountain Copper Company, at Martinez, California. This company for many years has been producing and marketing locally a super-phosphate, and some years ago endeavored to produce a high grade product. The possibility of making a high grade phosphate product has also been considered and discussed by the technical staff of the American Smelting and Refining Company in connection with their acid plant at Garfield, Utah. At Anaconda during the past two years a consistent and elaborate investigation with a high grade phosphate product in view has been made. The desire has been to obtain an outlet for the waste sulphur dioxide gas of the smelter through the production and utilization of sul- phuric acid. The investigation was started on a small scale in the laboratory, and is now advanced to the point where a unit of 500 pounds of phosphate rock per day capacity is being operated. Stated briefly, the results obtained up to the present time are as follows : Decomposition of the phosphate rock containing from 30 to 33 per cent. P 2 5 has been effected by grind- ing with dilute sulphuric acid, agitation with acid, or treatment with acid in a "den," as in the manufacture of ordinary super-phosphate. The best recoveries have been made by using the "den" decomposition followed by leaching. The rock is first treated with nearly the theoretical amount of sulphuric acid in a "den" to take care of the lime. The mixture ' ' sets ' ' after a few minutes stirring and usually is allowed to stand covered for 16 hours at about 40 C. The mixture is then leached with solutions from previous teachings containing about 6 per cent, sulphuric acid. The material filters quite satisfactorily ^Communicated by A. E. Wells of the Mine Experiment Station of the Bureau of Mines at Salt Lake City, Utah. 69 when the sulphuric acid content of the leaching solution is properly maintained, and the resulting 1 solution may contain as high as 20 per cent. P L ,O-. The extraction is about 90 per cent of the P 2 3 in the rock. In one line of investigation the solutions were evap- orated to about 45 per cent. P 2 0.-,, at which concentration some calcium sulphate was deposited. This phosphoric acid solution was then added to more phosphate rock, the amount of rock used being about 80 per cent, of that theoretically required to combine with the phosphoric acid, according to the reaction: Ca : ,(PO 4 ) 2 +4HoPO i 3CaH 4 (P0 4 )o. The mixtiue \vas alio\v< d t;> stand for sev- eral hours and then dried. A. , and continues to deposit as the concentration increases. In the laboratory all evaporations were effected in lead or glass, as the dilute solutions corroded iron rapidly. In some long-time evaporations, a glacial acid, a mixture of pyro and meta phosphoric acM resulted, containing as much as 70 to 80 per cent. P 2 n . Experiments are in progress in connection with the work now being conducted on the 500-pound unit, to detor- mino the possibility of evaporation in a tower such as is used in sulphuric acid concentration. At the Bureau of Mines experiment station in Salt Lake City, tests are in progress to determine whether the solution can be evaporated to a dry P ? r> powder by spraying the dilute or partially evaporated solutions into a stream of hot gases and precipitating the dehydrated acid by electrical profvrvta+ion methods. The evaporation problem still remains the most serious one in the production of a high grade phosphoric acid liquor or of glacial phosphoric ac?d. Due to the hvgrosconic pror>erties of the glacial acid, and the necessitv of shipping it in sealed, iron con- tainers, it is believed that it will be most feasible to 70 prepare a 60 to 65 per cent. P 2 5 solution to be shipped in tank cars. The possibility of substituting this phosphoric acid solution for sulphuric acid in the recovery of ammonia at the by-product coke plants with the production of am- monium phosphate, is being investigated. No data from this investigation are yet available. Though it is true that the grade of rock on which work has been done contains fairly high percentages of phosphoric acid, theie is in MOM tana, witliin a distance of 30 miles of the Anaconda smelter, large deposits of phosphate rock which will average only about 23 per cent, P 2 r ,, and in time it is likely that these deposits will be of considerable value. At the present time the phosphoric acid solutions from this grade of rock con- tain so much iron and alumina that it has been felt that it would be much better to work out the problem with the use of the higher grade rock, of which a great deal is present and can be easily mined in southern Idaho and northern Utah. ELECTRICAL METHODS. An interesting and recent development in the utili- zation of low grade phosphate rock is in the production of phosphoric acid and its derivatives, ammonium phos- phate and double super-phosphate, by utilization of the electric furnace. Sulphuric acid is here replaced by silica, coke, and electric energy, and with very cheap electric energy, the resulting product may be produced considerably cheaper and in a much more available form than by the present methods. The fertilizers- produced with the aid of electric energy, fixed nitrogen and avail- able phosphoric acid, go hand in hand with cheap water power. Ross, Carothers, and Merz* have recently summar- ized the results of certain experiments in the use of the Cottrell precipitator in recovering phosphoric acid evolv- ed in the volatilization method of treating phosphate rock by ignition with coke and silica in an electric furnace. "A current of air which was passed over the *Ross, W. H., Carothers, J. N., Mf-r?, A. R. T'-p use of the Cottrell precipitator in recovering- the phosphoric acid evolved in the volatiliza- tion method of treating" phosnhate rock. Journal of Industrial and Engineering- Chemistry, Vol. IX., No. 1, January 1, 1917, pp. 26-31. 71 charge in the furnace served the double purpose of oxidizing the fumes of phosphorus to phosphorus pentox- ide and of carrying the latter to the precipitator. In one series of experiments the fumes from the furnace before entering- the precipitator were passed through a tower provided Avith baffle plates which had the effect of cool- ing- down the gases to about ordinary temperature. Tn a second series of experiments the tower was cut out and the fumes passed almost directly into the precipitator at a temperature above 100 C. In each case the phos- phorus pentoxide, which takes up water from the current of air passing through the furnace and also from the moisture driven off from the charge, is precipitated in the form of a solution of phosphoric acid. When the precipitation is made at temperatures about 100, or above, the concentration of the acid is greater than that collected at a lower temperature, but by reducing the flow of air through the furnace, acid of high concentration may also be obtained with low temperature precipita- tion. 44 The advanutages of this method of collecting the phosphoric acid over the scrubbing tower method now in use 4 are as follows: "1. The equipment required is simple in construc- tion and automatic in operation. "2. The simplicity of the construction of the pre- cipitating pipes decreases the difficulties arising from the corrosive action of the phosphoric and hydrofluoric acids evolved from the phosphate rock. "3. In this way there may be recovered phosphoric acid of a high degree of purity suited for direct use with- out further purification in those industries where a rela- tively pure acid is required. "4. A more concentrated acid can be obtained in this way than is possible to prepare directly by any other commercial process, and when this acid is used in the preparation of concentrated fertilizers, such as mono-ammonium phosphate, a dry product may be ob- tained directly without the necessity of evaporating so- lutions, or of drying the resultant product. "This is the first time that the Cottrell precipitator has been used for the precipitation of a product which 72 has been purposely volatilized with a view to its recovery in this way." The fertilizer division of the Bureau of Soils has given considerable attention to the preparation of con- centrated fertilizers and a paper recently prepared by William H. Ross and Albert R. Merz* gives a general ac- count of some methods which may prove to be applicable in their preparation. The one which concerns this paper more especially relates to the preparation of phosphoric acid together with potassium and ammonium phosphates. Practically the entire output of fertilizers in the United States is consumed east of the Mississippi river, and more than four-fifths of this consumption is in the states bordering on the Atlantic Ocean and the Gulf of Mexico. Our natural resources in phosphate rock, how- ever, occur in overwhelming preponderance in the far west.f "A serious problem presents itself in bringing these raw materials or products derived from them to the region of consumption, as the distances are great and the only means of transportation available, that by rail, is expensive. A partial solution of this problem is found in the production of concentrated fertilizers, whereby the ratio of the cost of transportation to the value of the material shipped is considerably diminished. "The simplest of these commercial fertilizers in chemical constitution is phosphoric acid. The processes which have been used commercially for the preparation of this acid may be conveniently divided into two classes, as follows: (1) Processes which involve treatment of the rock with a mineral acid such as sulphuric acid ; and (2) processes in which the phosphorus is evolved from the rock by ignition with silica and coke and its subse- quent conversion into phosphoric acid through oxidation and absorption of the anhydride in some form of scrub- bing tower. With the volatilization method it has been found possible to prepare an acid of greater concentra- tion than it is possible to obtain directly in any process of the first group, but even in this process when the *Ross, W. H., and Merz, A. R. The preparation of concentrated fertilizers: The American Fertilizer. Vol. 45, No. 8, October 14, 1916, pp. 32-35. fSee paper by Phalen, W. C. The conservation of phosphate rock in the United States: Trans. Am. Inst. Min. Engrs., Bull. 119, November, 1916, pp. 1901-1934. 73 scrubbing tower method of recovering the phosphoric acid is used it is impractical to obtain an acid of greater strength than about 50 per cent, phosphorus pentoxide and evaporation must be resorted to for further concen- tration. However, if the scrubbing tower be replaced by a Cottrell prccipitator, no difficulty is found in securing phosphoric acid which contains upward of 95.0 per cent, phosphoric acid. A high grade phosphate rock of 75 per cent tricalciuin phosphate has 34.4 per cent. P^, whereas a 95.0 per cent, phosphoric acid solution con- tains 68.8 per cent P 2 5 . Therefore we have produced a fertilizer material twice as concentrated as high grade rock or over four times as concentrated as 16 per cent, super-phosphate and having all the P^O-, in the so-called available form. It may be interesting to note that this is the first time that the Cottrell precipitator has been used for llie precipitation of a product which has been purposely volatilized with a view to its recovery in this way. A detailed description of the experiments con- ducted with the precipitator and the advantages of its application are given in the paper referred to above. "The phosphoric acid which is produced by this procedure may be shipped directly in suitable containers to the region of fertilizer consumption, there to be used in the preparation of mixed fertilizers. This is now actually being considered by a western concern which contemplates shipping phosphoric acid that has been ex- tracted from western phosphates by the sulphuric acid method and concentrated by evaporation." The studies made by Ross and Mcrz also include the direct preparation of salts in which the phosphoric acid was combined with a fertilizer base such as potassium and ammonium to produce the corresponding potassium (KoP0 4 ) and ammonium phosphate ((NH 4 ) 3 P0 4 ). Methods of producing a concentrated fertilizer contain- ing all three fertilizer elements, that is nitrogen, potash, and phosphorus, are also outlined. THE FUTURE OUTLOOK FOP, THE KENTUCKY PHOSPHATE FIELD. From what has been stated with reference to the Kentucky phosphate field, it is evident that rock of high grade has been found in different places in the blue grass 74 region of central Kentucky, and without doubt many more workable deposits will be found as the entire region is systematically and carefully prospected according to the methods usually employed in this work and outlined in this paper. A somewhat restricted district in the vicinity of Wallace, a few miles south, southeast and southwest of Midway, Woodford County, is the only one of prom- inence within which phosphate rock is found to occur to any great extent. Between Midway and Spring Station, along the Louisville and Nashville Railroad, and on cer- tain farms to the north of the railroad, is another area where phosphate rock has been found in some quantity. The limits of these areas have not been very accurately determined, but enough drilling has been done to indicate that very important deposits of phosphate rock should be expected to be found locally. When it is remembered that brown rock phosphate may run from 600 to 1,000 tons per acre per foot of thickness, small areas may prove of great importance if the phosphate deposits in them are thick enough and of good quality. Outside of the Wallace area and that to the west of Midway, phosphate rock is known to occur in and around Lexington, Fayette County, in the vicinity of George- town, Scott County, near the Forks of Elkhorn, Franklin county, near Versailles, Woodford County, and near Pine Grove Station, Clark County. The material collected from the drillings made in this field shows great variation in content of calcium phosphate, and the sections themselves also show great irregularity in the thickness of the phosphate bed. In the Wallace district, of the total number of analyses made of materials collected from drillings, about one-third showed a content of 50 per cent, or more of calcium phos- phate. Less than 10 per cent, of the total showed a con- tent between 60 and 70 per cent., and but 5 per cent, of the total showed more than 70 per cent. The latter ma- terial was, for the most part, collected from well exposed sections in the old workings of the Central Kentucky Phosphate Company, near Wallace. The remaining: 65 ppr cent, contained less than 50 per cent, calcium phos- phate, and the great bulk of the material carried from 30 to 50 per cent. The other localities in which prospect- 75 ing" was carried on showed approximately similar re- sults. Occasional occurrences of lump rock were found in this area, containing more than 80 per cent, calcium phosphate, and although rock in workable quantity may be found running up to and above present commercial requirements, that is, containing 70 per cent, and more calcium phosphate, it is quite safe to affirm that the bulk of Kentucky rock will be found to contain less than 70 per cent. BPL. This means that in the most promising areas the rock will have to be carefully washed and cheaply worked by the most modern, labor saving de- vices, to bring it up to present commercial standards so that it will be able to compete in the open market with Tennessee rock. Without doubt, much of the Kentucky rock of low or intermediate grade must wait for cheap chemical or electrical processes of concentration. Some of the very latest developments in these processes are described^ in this paper. The Kentucky phosphate field is practically a virgin field. From its study and a comparison of it with the Tennessee field, it is felt that local conditions are sim- ilar and the problem of working the Kentucky phosphate deposits must be along much the same lines as in Ten- nessee. For this reason, brief descriptions of the tech- nology of the mining and preparation of phosphate rock for market as practiced in the Mt. Pleasant district of Tennessee are given. The advantages of the Kentucky field with respect to transportation rates to markets in the north and west are pointed out. Though the Kentucky field has an ad- vantage in freight rates to important fertilizer markets in Ohio, Indiana and Illinois, this has not led to the es- tablishment of any important industry in the State thus far. The Tennessee field, the pioneer, has enjoyed the advantages usually accruing to the first in the field. The Tennessee rock, on the average, is a higher grade rock than the Kentucky, which gives the former certain ad- vantages, until effective concentration methods, either mechanical, chemical, or both, are introduced in the Ken- tucky field. The lands on which the Kentucky rock phosphate has been found are very fertile, in fact are the most 76 fertile in the blue grass region. Consequently they possess high values for farm and grazing purposes, and are worth at least $200 per acre for these purposes alone. The extent to which the Kentucky field will be developed depends not only on what may underlie the land, but on the attitude assumed by the farmers who own it. Whether it is considered more valuable for farming purposes than for the phosphate deposits which underlie it in places, re- mains to be seen, assuming, of course, that exact knowl- edge with regard to its mineral wealth becomes better known as time goes on. It is certain that after mining operations have been conducted it will cost much to bring the land into condition for farming, if this can be done at all. In this connection, however, it is of interest to point out that in Tennessee, whore hydraulic mining is practiced in one locality, the rock is mined out in a small area and the overburden from that next to it is washed into the area which has been mined out. The resultant topography is level and may be farmed over again, a most important consideration where the land is as valuable as in the Kentucky Blue Grass region. Ac- cording to this method of removing overburden, the land is conserved for farming purposes for future genera- tions and greatly improved at the same time, for a part of the phosphate rock and sand formerly below the sub- soil is thoroughly incorporated into the top soil, and the fertilizer value of the phosphate rock thus rendered available in time. Many extensive deposits of low grade Kentucky rock may be expected to become profitable in the future, as methods for their practical utilization are solved, and as the supply of high grade rock in other eastern states shall have become exhausted. BIBLIOGRAPHY OF PUBLICATIONS RELATING TO PHOSPHATE ROCK. BAKU. JAMES A., Tennessee phosphate practice: Trans. Am. Inst. Min. Engrs., Bull. 93, Sept., 1914, pp. 2397-2413. - The use of low grade phosphate: Trans. Am. Inst. Min. Engrs., Bull. 110, Feb., 1916, pp. 243-245. Bi.AcivWKi.DEK, ELIOT, Phosphate deposits east of Ogden, Utah: U. S. Geol. Survey, Bull. 430, pp. 536-551, 1910. - A reconnaissance of the phosphate deposits in western Wyom- ing: U. S. Geol. Survey Bull. 470, pp. 452-481, 1911. C n ATARI). T. M., Phosphate chemistry as it concerns the miner: Trans. Am. Inst. Min. Engrs., Vol. XXL, pp. 160-175, 1893. DARTOX. N. H., and SIEKEXTIIAL. C. E., Geology and mineral resources of the Laramie Basin, Wyo.; a preliminary report: U. S. Geol. Survey Bull. 364, pp. 81, 1909. ECKEL, E. C., Recently discovered extension of Tennessee white-phos- phate field: U. S. Geol. Survey Mineral Resources, 1900 pp. 812-813, 1901. - Utilization of iron and steel slags: U. S. Geol. Survey Bull. 213, pp. 221-231, 1903. - The white phosphates of Decatur County, Tenn.: U. S. Geol. Survey Bull. 213, pp. 424-425, 1903. Ei.iminGK. G. H., A preliminary sketch of the phosphates of Florida: Am. Inst. Min. Eng. Trans., Vol. 21, pp. 196-231, 1893. FOKHSTK. A. E., The phosphate deposits in the upper Trenton lime- stones of Central Kentucky: Ky. Geol. Survey, Series IV., Vol. I., Part I., 1913, pp. 391-439. GALE, H. S., Rock phosphate near Melrose, Mont.: U. S. Geol. Survey Bull. 470, pp. 440-451, 1911. GALE, H. S., and RICIIAKMH, R. W., Preliminary report on the phosphate deposits in southeastern Idaho and adjacent parts of Wyoming and Utah: U. S. Geol. Survey Bull. 430, pp. 457-535, 1910. GARDNER. JAMES H., Rock phosphate in Kentucky: Mines and Minerals, November, 1912, pp. 207-209. GIRTY, G. H., The fauna of the phosphate beds of the Park City formation of Idaho, Utah, and Wyoming: U. S. Geol. Survey Bull. 436, 82 pp., 1910. HAYES, C. W., The Tennessee phosphates: U. S. Geol. Survey, Sixteenth Ann. Rept., pt. 4, pp. 610-630, 1895; Seventeenth Ann. Rept., pt. 2, pp. 519-550, 1896. The white phosphates of Tennessee: Am. Inst. Min. Eng. Trans., Vol. 25, pp. 19-28, 1896. 78 - A brief reconnaissance of the Tennessee phosphate field: U. S. Geol. Survey, Twentieth Ann. Kept., pt. 6, continued, pp. 633-638, 1899. - The geological relations of the Tennessee brown phosphates: Science, Vol. 12, p. 1005, 1900. - Tennessee white phosphate: U. S. Geol. Survey, Twenty-first Ann. Kept., pt. 3, pp. 473-485, 1901. - Origin and extent of the Tennessee white phosphates: U. S. Geol. Survey Bull. 213, pp. 418-423, 1903. HOOK, J. S., The brown and blue phosphate rock deposits of South Cen- tral Tennessee: The Resources of Tennessee, Vol. IV., No. 2, April, 1914, pp. 51-83. - The white phosphates of Tennessee: The Resources of Tennes- see, Vol. V., No. 1, January, 1915, pp. 23-33. IHLSENG, M. C., A phosphate prospect in Pennsylvania: U. S. Geol. Sur- vey, Seventeenth Ann. Rept., pt. 3, continued, pp. 955-957, 1896. MATSOX, G. C., The phosphate deposits of Florida: U. S. Geol. Survey Bull. 604, pp. 101, 17 pis., 1915. MANSFIELD, G. R., A reconnaissance for phosphate in the Salt River Range, Wyo.: U. S. Geol. Survey Bull. 620, pp. 331-349, 1915. MAYNAKD, T. POOLK, White rock phosphates of Decatur County, Tennes- see: The Resources of Tennessee, Vol. III., No. 3, July, 1913, pp. 161-169. MEMMINGEU, C. G., Commercial development of the Tennessee ph6s- phates: U. S. Geol. Survey, Sixteenth Ann. Rept., pt. 4, pp. 631-635, 1895. MILLER, A. M., The association of the gastropod genus cyclora with phosphate of lime deposits: Am. Geologist, Vol. XVII., Feb., 1896, pp. 74-76. - Safford on Tennessee phosphate: Am. Geologist, Feb., 1894, Vol. XIII., No. 2, pp. 107-109. MOSES, O. A., The phosphate deposits of South Carolina: U. S. Geol. Survey Mineral Resources, 1882, pp. 504-521, 1883. PARDEE, J. T., Some further discoveries of rock phosphate in Montana: U. S. Geol. Survey Bull. 530, pp. 285-291, 1913. PEXROSE, R. A. F., Nature and origin of deposits of phosphate lime: U. S. Geol. Survey Bull. 46, 143 pp., 1888. PIIALEX, W. C., Phosphate rock: U. S. Geol. Survey Mineral Resources, 1912, pt. 2, pp. 855-876, 1913; idem., 1913, pt. 2, pp. 273-289, 1914; idem., 1914, pt. 2, pp. 41-56, 1915. The conservation of phosphate rock in the United States: Trans. Am. Inst. Min. Engrs. Bull., No. 119, Nov., 1916, pp. 1901-1913. PURDUE, A. H., Developed phosphate deposits of northern Arkansas: U. S. Geol. Survey Bull. 315, pp. 463-473, 1907. RICHARDS, R. W., and MAXSFIELD, G. R., Preliminary report on a por- tion of the Idaho phosphate reserve: U. S. Geol. Survey Bull. 470, 'pp. 371-439, 1911. 79 RICHARDS, R. W., and MANSFIELD, G. R., Geology of the phosphate de- posits northeast of Georgetown, Idaho: U. S. Geol. Survey Bull. 577, 76 pp., 14 pis., 1914. ROGERS, G. S., The phosphate deposits of South Carolina: U. S. Geol. Survey Bull. 580, pp. 183-220, 1914. Sc iiri/rz, A. R., Geology and geography of a portion of Lincoln County, Wyo.: U. S. Geol. Survey Bull. 543, pp. 131-134, 1914. ScHUJ/rz, A. R., and RICHARDS, R. W., A geologic reconnaissance in southeastern Idaho: U. S. Geol. Survey Bull. 530, pp. 267-281, 1913. SMITH, G. O., and others, The classification of the public lands: U. S. Geol. Survey Bull. 537, pp. 123-134, 1913. STOXE. R. W. and BOXIXK, C. A., The Elliston phosphate field, Montana: U. S. Geol. Survey Bull. 580, pp. 373-383, 1914. STOSK, G. W., Phosphorus ore at Mount Holly Springs, Pa.: U. S. Geol. Survey Bull. 315, pp. 474-483, 1907. - Phosphorus: U. S. Geol. Survey Mineral Resources, 1906, pp. 1084-1090, 1907. - Phosphate deposits in southwestern Virginia: U. S. Geol. Survey Bull. 540, pp. 383-396, 1914. STI-JWS, W. C., Phosphates of Alabama: U. S. Geol. Survey Mineral Re- sources, 1883-84, pp. 794-803, 1885. VAX HORX, F. B., The phosphate deposits of the United States: U. S. Geol. Survey Bull. 394, pp. 157-171, 1909. - Phosphate rock: U. S. Geol. Survey Mineral Resources, 1911, pt. 2, pp. 877-888, 1912. WAGGAMAX, W. H., A review of the phosphate fields of Florida: U. S. Dept. of Agriculture, Bureau of Soils, Bull. 76, 1911. - A report on the phosphate fields of South Carolina: Bull, of the Dept. of Agriculture, No. 18, 1^13. WAGGAMAX, W. H., and FRY, W. H., Phosphate rock and methods pro- posed for its utilization as a fertilizer: U. S. Dept. of Agriculture, Bull. 312, 1915. WKEKS, F. B., Phosphate deposits in the Western United States: U. S. Geol. Survey Bull. 340, pp. 441-447, 1908. WEEKS, F. B., and FERRIER, W. F., Phosphate deposits in western United States: U. S. Geol. Survey Bull. 315, pp. 449-462, 1907. WILBER. F. A., Greensand marls in the United States: U. S. Geol. Sur- vey Mineral Resources, 1882, pp. 522-526, 1883. 80 Plate I. View of Brannon cherty limestone with upper contorted limestone layer and overlying phosphate rock debris. Cut on Queen & Crescent Route near Virginia Avenue bridge, Lexington, Ky. Plate II. View showing irregular bedding in the Brannon cherty limestone near Virginia Avenue bridge, Lexington, Ky. Plate III. Crushed zone in limestone in the Brannon member. East side of Versailles-Frankfort pike, about 3 miles north of Versailles, Woodford County, Ky. Plate IV. Old McMeekin limestone quarry, Newtown pike, 3 miles north of Lexington, Ky. In this quarry Dr. R. Peter first noted the association of cyclora and phosphate rock. Plate V. Arching of phosphate rock over limestone horse. Note the band- ing in the phosphate rock and also in the limestone. United Phosphate and Chemical Co., near Wallace, Ky. Plate VI. Arching of phosphate rock beds over underlying limestone. United Phosphate and Chemical Company, near Wallace, Ky. Plate VII. Limestone with interlaminated phosphatic layers. Type of rock from which phosphate deposits are derived. Quarry on Haggin estate, east, of Maysville pike, 7 miles northeast of Lexington, Kentucky. Plate VIII. Alternating layers of limestone and phosphatic material, Mt. Pleasant, Tenn. Plate IX. View in old phosphate workings showing "cutters" and limestone "horses." Near Wallace, Ky. Plate X. Arching of phosphate rock over limestone horses. Near Mt. Pleasant, Tenn. Plate XI. Rafinesquina alternata from near Versailles, Woodford County, Ky. The shell has been replaced by SiO 2 and Ca 3 (PO 4 ) 2 has infiltrated and formed a cast of the interior of the shell. Plate XII. Removing overburden with scrapers. Near Scotts Mill, Maury County, Tenn. Plate XIII. Distant view of a cantilever, showing an open pit in part worked out, Mt. Pleasant, Tenn. Note the method of disposing of overburden; limestone horses, cutters, and phosphate rock curving over horses. Plate XIV. A typical drag line excavator at work stripping overburden. Mt. Pleasant, Tenn. Plate XV. A steam shovel removing overburden, Mt. Pleasant, Tenn. Plate XVI. Mining phosphate rock with hydraulic gun, near Mt. Pleasant, Term. Overburden is also removed by this method. Plate XVII. Drying phosphate rock by burning in open kilns, Mt. Plea-sant, Tenn. Plate XVIII. A deep and wide cutter. Shows the method of removing phosphate rock by hand from deep cutters. Mt. Pleasant, Tenn. Plate XIX. A very narrow cutter from which it is difficult to remove the phosphate, rock, Mt. Pleasant, Tenn. $he phosp ceTitrai~~K ate rocks of .376 UNIVERSITY OF CALIFORNIA LIBRARY