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Home > California > CA - Quarry Links & Photographs > El Dorado County > List of Quarries > Kelsey (Only)
"The California-Bangor Slate Company Mine was located one mile northwest of Kelsey. It was active prior to 1915."
"Eureka Slate Company, Wm. J. Dingee, president, Crocker Building, San Francisco, is operating the quarry that is producing any slate at present in California. It is located at Slatington, one mile south of Kelsey, and between 7 and 8 miles north from Placerville, the nearest railway station and the shipping point of the slate. The quarry has been in operation for fifteen or twenty years. The present company has operated it only about two years and a half, and has put in large improvements, among others an extended wire cable-way 3 miles long, of the Bleichert system, for transporting the slate across the American River, with a clear span across the river-valley of 2400 feet, at an elevation of 600 feet above the river, and operated by water-power. From the south end the slate is hauled by wagon to the railway at Placerville.
"The Eureka slate has a blue-black color, which weathers brown in some places, and greenish-gray in other places. It is for the most part free from impurities in the deeper portion of the quarry, but in a few places there is iron pyrite along the seams and a few small quartz and calcite veins, which add to the waste that is always an important part of every slate quarry.
| Ill. No. 69. Eureka Slate Quarry, Slatington, El Dorado County. |  |
| Ill. No. 70. View in yard near quarry of the Eureka Slate Company, El Dorado County. |  |
"The quarry is located in the bottom and on both sides of a small cañon. The steep slope for several hundred feet below the quarry opening gives an excellent dumping ground for the waste product. The quarry opening on the north side of the cañon has been abandoned. On the south side of the cañon the quarry has a face over 200 feet long, and about 70 feet high at one end, and about 200 feet at the other. The west end of the quarry has been sunk 90 feet below the bottom of the cañon. The deep portion is about 100 feet square, and it is from this opening that the greatest quantity of good slate, with the least waste, is now obtained. The east end of the quarry is within 40 feet of the bottom of the cañon. From both places large quantities of good roofing slate are quarried.
"The strike of the cleavage is south 25 degrees east. To a depth of nearly 40 feet in places, there are numerous joint-planes cutting the slate into small dimensions. Below this the joints rapidly disappear, and in the bottom portions there are very few - not enough to interfere with taking out blocks as large as can be quarried and handled. The blocks are loosened by hand work, by drilling and wedging, and are then lifted by the cable-hoists and placed on cars on the tracks on the upper floor. The same hoists are used to lift the fragments and waste. The blocks taken out vary from 300 to 3000 pounds in weight.
"The marketable slate is run to the sheds, where the splitters and the blockmaker reduce it to the standard size for roofing. The finished slate is placed in small iron carriers on the cable-way. The present output is 1000 squares per month.
"The entire product is used for roofing slate, for which purpose it gives good satisfaction and the demand keeps pace with the shipments. The slate unit is the square which is sufficient to cover 100 square feet of roof, and weighs about 600 pounds.
"Running through the body of the slate are numerous narrow ribbons of a material more siliceous than the adjoining slate, which are separated in the quarry operation and thrown out in the waste. These ribbons do not follow the cleavage of the slate, but indicate the original bedding of the slate mass, which does not vary greatly at this point from the cleavage plane.
Eureka Green Slate. There is a green-colored belt of slate several feet in width, crossing the black slate, that is thought by Mr. Eckel* to be an altered intrusive dike of igneous rock. This is indicated by the fact that it is not parallel to the ribbons and hence is not interstratified material, and further by the chemical composition., which shows it to be quite unlike the black slate and much like certain basic igneous rocks of the district. The green slate is not quite so smooth as the black, but works very well and is used with the black for lettering and trimming."
(* Footnote: Bulletin No. 225, U. S. Geological Survey, p. 419.)
| Map - Geologic Map of Placerville Slate District, California. Plate X (From Slate Deposits and Slate Industry of the United States, Bulletin No. 275, 1906.) |  |
"Location and general relations. – Though roofing slate has at different times been quarried on a small scale in other parts of California, the only important slate-producing area in the State is located in Eldorado (sic) County. The quarries which have been opened in this district are located along a line running about N. 15 W. from Placerville, at distances of 1 to 6 miles from that town. The location and geographic and geologic relations of the slate deposits and quarries can best be understood by reference to the maps included in the Placerville folio of the United States Geological Survey…."
"Previous work on the slate deposits. – The Placerville folio, No. 3, United States Geological Survey, published in 1894, contains the results of detailed geologic work by Lindgren and Turner in the area in which the roofing-slate deposits occur. At that date the roofing-slate industry had not assumed its present importance, though all the quarries now worked (circa 1906) had then been opened. The existence of roofing-slate deposits is noted in the text of the folio, and the locations of the quarries are indicated on the map showing the economic geology of the area. No reference is made to the 'green slates,' or to the dikes cutting the Eureka quarry.
"Excellent though brief descriptions of the different quarries and of the condition of the slate industry at various dates are to be found in the reports of the State mineralogist of California, particularly in the eighth and twelfth reports. The geologic relations of the slate-producing areas are shown in Pl. X.
"At present (circa 1906) the most important quarry is that of the Eureka Slate Company, and this is now being worked on a large scale. This quarry is at Slatington, about one-half mile southwest of Kelsey.
Structural relations in Eureka quarry. – The overturning planes of the slates in the Eureka quarry strike N 25 W. The dip of the cleavage is practically vertical, with slight local variations to 80 E. or 80 W. The upper weathered beds in the quarry are overturned by local pressure so as to give dips of 40 to 60 to the east or west, according to local conditions. This overturning is evidently due merely to the weight of the overlying soil and decomposed slate, and the effects are shown only for a depth of from 3 to 15 feet. It is of interest, however, as of warning against accepting dip readings taken from surface beds of the slate.
"The slate body shows rather frequent, but narrow, 'ribbons.' These ribbons are bands (from one-sixteenth to one-half inch thick usually, but occasionally as thick as 2 inches) of material differing in composition from the mass of the slate. They are in general more siliceous than the normal slate, and do not furnish merchantable material. Their geologic interest arises from the fact that they represent differences of original sedimentation. The plane of the ribbons in a slate quarry is, therefore, the plane of the original bedding. In the Eureka quarry, and, indeed, throughout the roofing-slate belt, the plane of original bedding seems to be usually within 10 of the plane of slaty cleavage.
"The slate mass is cut by a series of joints parallel to the 'grain' of the slates, striking N. 55 E. and dipping from 70 to 80 NW. Joints across the 'grain' of the slate, which would be practically horizontal, do not occur in this quarry, but many of the thin quartz seams occupy this position.
"Quartz and calcite occur in thin layers, filling joint spaces and occasionally cleavage spaces. Pyrite also occurs in very much flattened nodules, which were apparently parallel to the original bedding.
Character of the normal slate. – "The mass of the Eureka quarry product is a dense, deep-black slate, splitting very finely and regularly, with a smooth glistening surface, much like that of the Bangor and Lehigh slates of Pennsylvania. The frequency of the ribbons and of the pyrite nodules prevents the slate from being serviceable as mill stock, but as a roofing material it is excellent.
"A specimen of the black slate, free from ribbon, was selected for analysis in the laboratory of the United States Geological Survey. The results of this analysis by Mr. W. T. Schaller, follow:
"Prof. T. Nelson Dale has reported as follows on a sample of this slate:
"This slate is very dark gray. To the unaided eye it has a fine texture and a smooth and lustrous cleavage surface. It contains considerable carbonaceous or graphitic material. There is no effervescence in cold dilute hydrochloric acid. It is sonorous and has a high grade of fissility.
"Under the microscope it shows a matrix of muscovite (sericite) with a brilliant aggregate polarization and a general evenness of texture, interrupted, however, by lenses up to about 8 mm. long by about one-half mm. wide, consisting chiefly of quartz fragments (surrounded by a rim of radiating secondary quartz) with muscovite scales, plates, and rhombs of carbonate, and rarely a grain of plagioclase. These lenses have their long axes parallel to the cleavage, but in sections parallel to it some of them have such irregular outline and are so large as to appear like minute beds. The matrix contains many quartz fragments, measuring up to 0.09 by 0.03 mm., much less carbonate than the lenses, muscovite scales, chlorite scales, a little pyrite in spherules and crystals, carbonaceous or graphitic matter, ruttile needles, a few grains of tourmaline, and rarely one of zircon.
"This ought to prove a serviceable slate. It will be noticed that carbonate, although present, is insufficient to produce effervescence.
"Eureka quarry green slate.* – A band of green slate several feet wide crosses the Eureka quarry. On examination it is found that the borders of this band are not parallel to the 'ribbon' of the black slate. The green band can not, therefore, be interbedded with the black slates. The probability that it represents a dike of massive igneous rock which has been changed to a slate by pressure subsequent to its intrusion is strengthened when the chemical composition of the green slate is considered. Two analyses of the green slates are presented on the next page. The first is of a sample selected by the writer and analyzed in the laboratory of the United States Geological Survey by Mr. W. T. Schaller; the second was given by Mr. C. H. Dunton, manager of the Eureka quarry, but the name of the analyst is unknown. As the analyses show a close agreement in essential features, it is probable that they are fairly representative of the composition of the green slates, and that their average, which is given in the third column of the table, may be regarded as typical of this interesting and apparently unique type of roofing slate.
(* Page 57 footnote a: For a more detailed discussion of this interesting "igneous slate" the reader is referred to the paper by the writer in the Journal of Geology, vol. 12, 1904, pp. 15-29.)
"These analyses have been compared* with a series of 36 analyses of American roofing slates derived from clays by pressure, and remarkable differences in composition are apparent. The green slate, on the other hand, approximates closely in composition to certain 'basic' igneous rocks of the district, and it is probably that it was derived from a gabbro or similar rock.
(* Page 58 footnote a: Jour. Geol., vol. 12, 1904, p. 26.)
"The 'green slate' is in reality grayish green in color. It splits readily, though with not so smooth a surface as the black slate. It stands punching and trimming well, and is sufficiently strong for roofing use. Considering its origin and composition it is probable that it will be a highly durable slate, holding its color well. At present (circa 1906) it is sold entirely for trimming and lettering on black slate roofs, for which purpose it is particularly well adapted, giving a strong but pleasant color contrast.
"Transportation and market. – The Eldorado (sic) County slates have practically no competition on or near the Pacific coast, while the Eureka quarry has recently placed large shipments in Hawaii and Guam. Until recently the principal problem has been the transportation of the slates from the quarry to the railroad. This was formerly done by wagon hauling over a 6-mile stretch of very hilly road. During the last season, however, the Eureka Slate Company has installed an aerial tramway system from its quarry to a point near Placerville. This tramway is an engineering feat of no mean order, the crossing of the South Fork of American River being the principal difficulty encountered."
(* NOTE: This 1914 report is essentially the same as the 1906 report in Slate Deposits and Slate Industry of the United States, Bulletin No. 275, "Slate Deposits and Industry of the United States - California, by Edwin C. Eckel, pp. 56-59, Department of the Interior, United States Geological Survey, Washington: Government Printing Office, 1906." There are if, if any, changes made to the original 1906 report.)
| Plate X. Geologic Map of Placerville Slate District, California, from U.S. Geological Survey Atlas, folio 3. |  |
"Structural relations in Eureka quarry. – At present (circa 1914) the most important quarry is that of the Eureka Slate Co., and this is now being worked on a large scale. This quarry is at Slatington, about half a mile southwest of Kelsey. The cleavage planes of the slates strike No. 25 W. The dip of the cleavage is practically vertical, with slight local variations to 80 E. or 80 W. The upper weathered beds in the quarry are overturned by local pressure as to give dips of 40 to 60 to the east or west, according to local conditions. This overturning is evidently due merely to the weight of the overlying soil and decomposed slate, and the effects are shown only for a depth of 3 to 15 feet. It is of interest, however, as a warning against accepting dip readings taken from surface beds of the slate.
"The slate body shows rather numerous but narrow 'ribbons.' These ribbons are bands (from one-sixteenth to one-half inch thick usually, but locally as thick as 2 inches) of material differing in composition from the mass of the slate. They are in general more siliceous than the normal slate and do not furnish merchantable material. Their geologic interest arises from the fact that they represent differences in original sedimentation. The plane of the ribbons in a slate quarry is therefore the plane of original bedding. In the Eureka quarry and indeed throughout the roofing-slate belt the plane of original bedding seems to be usually within 10 of the plane of slaty cleavage.
"The slate mass is cut by a series of joints parallel to the grain of the slates, striking N. 55 E. and dipping 70 -80 NW. Joints across the grain of the slate, which would be practically horizontal, do not occur in this quarry, but many of the thin quartz seams occupy this position. Quartz and calcite occur in thin layers, filling joint spaces and some cleavage spaces. Pyrite also occurs in very much flattened nodules, which were apparently parallel to the original bedding.
"Character of the normal slate. – The mass of the Eureka quarry product is a dense deep-black slate, splitting very finely and regularly, with a smooth glistening surface, much like that of the slates of Lehigh and Northampton counties, Pa. The abundance of the ribbons and of the pyrite nodules prevents the slate from being serviceable as mill stock, but as a roofing material it is excellent…."
"Green slate of Eureka quarry.* – A band of green slate several feet wide crosses the Eureka quarry. On examination it is found that the borders of this band are not parallel to the ribbon of the black slate. The green band can not, therefore, be interbedded with the black slate. The probability that it represents a dike of massive igneous rock which has been changed to a slate by pressure subsequent to its intrusion is strengthened when the chemical composition of the green slate is considered. Two analyses of the green slates are presented below. The first is of a sample selected by the writer and analyzed in the laboratory to the United States Geological Survey by W. T. Schaller; the second was given by Mr. C. H. Dunton, manager of the Eureka quarry, but the name of the analyst is unknown. As the analyses show a close agreement in essential features, it is probable that they are fairly representative of the composition of the green slate, and that their average, which is given in the third column of the table, may be regarded as typical of this interesting and apparently unique type of roofing slate…."
(Page 68 footnote 1: For a more detailed discussion of this interesting "igneous slate" the reader is referred to a paper by the writer in the Journal of Geology, vol. 12, pp. 15-29, 1904.)
(Page 68 footnote 1: For a more detailed discussion of this interesting "igneous slate" the reader is referred to a paper by the writer in the Journal of Geology, vol. 12, pp. 15-29, 1904.)
"These analyses have been compared* with a series of 36 analyses of American roofing slates derived from clays by pressure, and remarkable differences in composition are apparent. The green slate, on the other hand, approximates closely in composition certain 'basic' igneous rocks of the district, and it is probable that it was derived from a gabbro or similar rock.
(* Page 68 footnote 2: Jour. Geology, vol. 12, p. 26, 1904.)
"The 'green slate' is in reality grayish green in color. It splits readily, though with not so smooth a surface as the black slate. It stands punching and trimming well and is sufficiently strong for roofing use. Considering its origin and composition, it is probable that it will be a highly durable slate, holding its color well. At present (circa 1906) it is sold entirely for trimming and lettering on black slate roofs, for which purpose it is particularly well adapted, giving a strong but pleasant color contrast…."
"Transportation and market. – The slates of Eldorado County have practically no competition on or near the Pacific coast, and the Eureka quarry has recently (circa 1906) placed large shipments in Hawaii and Guam. Until recently the principal problem has been the transportation of the slates from the quarry to the railroad.* This was formerly done by wagon hauling over a 6-mile stretch of very hilly road. In 1905, however, the Eureka Slate Co. installed an aerial tramway system from its quarry to a point near Placerville. This tramway is an engineering feat of no mean order, the crossing of the South Fork of American River being the principal difficulty encountered."
(* As this 1914 report is essentially the same as the 1906 report in Slate Deposits and Slate Industry of the United States, Bulletin No. 275, "Slate Deposits and Industry of the United States - California, by Edwin C. Eckel, pp. 56-59, Department of the Interior, United States Geological Survey, Washington: Government Printing Office, 1906.," the shipments to Hawaii and Guam and the problem with the transportation by wagon occurred circa 1906 rather than nearer the published date of this report in 1914.)
"Eureka Slate Quarry. This property is situated 1 mile south of Kelsey and 7 miles north of Placerville. Comprises 640 acres of patented mineral land. The property was operated steadily from 1903 to 1909, and a very fine quality of roofing slate produced. The slate is blue-black in color, in the most part free from impurities, with a high tensile strength. The strike of cleavage is S. 25 E. The quarry opening on the north side of the cañon is 90' high by 200' long. The quarry on the south side of the cañon has a face over 200' long and 70' high on one end and 200' high on the other end. This quarry has been sunk to a depth of 90' below the cañon. The waste product from these quarries ran about 85%. The capacity of quarry when under operation was 100 squares of roofing slate per day.
"Equipment: 150 h.p. compressor, 5 hoisting engines, slate trimming machines, saw tables, rubbing bed and planers. The product was transported from quarry by an aerial tram across the American River to Placerville. This tram is 3 miles long, there being a distance of 13,000' between terminals, with 26,000' of drawing rope; was operated by 35 h.p. Pelton motor. Water was secured from the Truckee General Electric Co. ditch, by pipe line 1 ½ miles long; with a head of 500'. Since the property was visited, operations have been resumed under the personal supervision of W. J. Dingee, 898 Monadnock Bldg., San Francisco, owner."*
(* Page 307 footnote: "Since the above was written, it is stated that the Eureka Quarry has been sold (June, 1916) to the Sierra Slate Corporation, of New York. The new company expects to reopen the property on a large scale, and prepare for market from 1000 to 2000 squares per month. A 'Square' of slate is a sufficient number of pieces to cover 100 square feet of roof.")
| Eureka Slate Quarry, north of Placerville, El Dorado County. |  |
This quarry was operated by the Sierra Slate Company, and it was "located one mile south of Kelsey." It was active from about 1886 to 1926. According to Mr. Noble's article, "Dimension slate for a multitude of uses was mined from the quarry that had a 200-foot face and a depth of 200 feet. The mined slate was delivered to Placerville for transport on the railroad by means of a spectacular 13,000 foot long aerial tramway."
"One of El Dorado County's several slate mines was the Landeker Mine, located near Kelsey. It was active in the 1880's when roofing slate was produced."
This slate quarry "produced some of the highest quality roofing slate in the County, which was carried to Placerville by wagon and loaded on train cars. This quarry may be the same quarry called the Eureka Slate Quarry that ended up shipping dimension slate to Placerville by way of a 13,000 foot aerial tramway."
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