“The West Cool-Cave Valley Mine was a limestone mine one mile west of Cool-Cave Valley, near the Middle Fork of the American River. The deposit consisted of a lens 450 feet long and 50 feet wide, of bluish-gray, high-calcium limestone. Mining was by open pit.”
“Among the products of this county are lime, marble, copper, and iron. The lime quarries are the most valuable in the State, and have been successfully and profitably worked since 1853. They are located in what is known as Cave Valley, on the Georgetown Divide, and are of unlimited extent. The building of the narrow gauge road spoken of would make these quarries worth hundreds of thousands of dollars....”
“At Cave Valley, east of Auburn, is another limestone quarry and limekilns.”
"Cave Valley Limestone Quarry. See our Bulletin 38, p. 68. Situated 9 miles east of Newcastle, Placer County. The limestone is crystalline, granular, white, clouded white, and blue in color. Idle. H. Cowell, of San Francisco, owner."
"Cowell Cave Valley Deposit. Owner of this deposit is Henry Cowell Lime and Cement Company, 2 Market Street, San Francisco. It is in secs. 6, 7, and 18, T. 12 N., R. 9 E., M.D., 5 to 6 miles by good road east of Auburn. The total land holdings on this deposit cover 947 acres and the deposit extends for about 2 miles in length with an exposed width of 200 to 400 feet. It includes one large lens and part of another 1 ¼ miles on this property, the northern portion of the latter having been worked on an adjoining property for a part of at least every year from 1910 to 1942. It was mined in a large open pit up to the Cowell property line, and to a depth of 800 feet. This northerly lens was traversed by the Middle Fork of the American River and the canyon permitted operation to this depth by starting near the river level.
"Aside from their exceptional size, these limestone deposits are typical of the series of roughly lens-shaped bodies found in the Calaveras (Carboniferous, Mississippian) meta-sediments of this section of the Sierra Nevada. The series of beds have been folded and compressed so that the lenses of limestone stand nearly on edge, and where exposed by erosion they have the character of frozen veins. So general and intense has been the metamorphism that the limestone is all crystallized, firm to tenacious in texture, and generally devoid of visible organic remains, except for the finely divided carbonaceous residue which gives it the prevalent blue-gray to nearly black color, which is subdued by weathering to a typical dove-gray shade. But it is remarkable that, in spite of the metamorphism, every one of these deposits was found to be a 'stinkestein' (fetid limestone), giving a more or less pronounced odor on being hammered.
"Cool Valley Lime Company quarried the limestone on both sides of the Auburn-Cool road and made lime in two kilns 40 to 50 years ago. The workings were shallow, as the limestone outcrops there do not stand much higher than the general ground level. The fullest development without recourse to hoisting would require entry from the south side of the river canyon and if the south lens proved to extend as deep as the north lens, the tonnage of limestone in it alone to a depth of 500 feet would be sufficient to justify a plant of any size.
"The following analyses were of large samples taken by chipping good sized pieces at regular intervals, across the widths indicated:
Sample across 270 feet
Insoluble, 0.22 percent
Fe2O3 and A12O3, 0.25 percent
CaCo3, 98.50 percent
MgCo3, 0.34 percent
Total, 99.31 percent
Sample across 400 feet
Insoluble, 1.02 percent
Fe2O3 and A12O3, 0.29 percent
CaCo3, 98.14 percent
MgCO3, 0.45 percent
Total, 99.90 percent
"This property was leased to California Rock and Gravel Company, 1800 Hobart Building, San Francisco, in 1946 and at time of the author's visit in October 1946 was being worked for them under contract by E. B. Bishop. Several hundred tons of limestone was being shipped daily from Auburn.
"A face 50 feet high by 300 feet long has been opened on the limestone in section 7 about a quarter of a mile north of the highway. Five wagon drills are operated 2 shifts, drilling 30-foot holes on 6-foot centers. These are shot with 60 percent Atlas dynamite, as the limestone is tough and hard. Large blocks of stone are blasted small enough to load with 1 ½- and 2 ½-cubic-yard power shovels into trucks, which deliver limestone to the 30- by 42-inch primary crusher, which is set to 7 ½ inches and operated by 100-horsepower motor. From this it passes by belt conveyor to a trommel with 6-inch square holes, and oversize goes to secondary crusher. Another belt conveyor delivers all stone to a double-deck screen on top of the loading bins. This screen delivers two sizes, 2 inch by 4 inch and 4 inch by 6 inch to separate bins for loading into trucks which haul it to railroad cars at Auburn. The minus 2-inch material is carried by a belt conveyor to a stockpile. Bin capacity is 900 tons. Three portable air compressors are used, two drills requiring a 500-cubic foot compressor. Electric power is supplied by Pacific Gas & Electric Company.
"At present a 7-day week is worked and stone is being shipped to beet-sugar refineries, which require a large tonnage during their operating season, in autumn and winter. These refineries burn the limestone in vertical kilns, so demand a hard, fine-grained stone that will make good lump lime. This deposit, as shown in analyses of samples taken by the writer, is a very high-grad, high-calcium limestone, and according to Boyd Oliver, vice president of California Rock and Gravel Company, recent analyses have indicated over 99 percent CaCO3, with less than 0.025 percent iron.
"California Rock and Gravel Company took over operation of the property, doing considerable advance prospecting during the early part of 1947, followed by heavy production throughout the dry season."
|Frontispiece. Aerial view of Cool-Cave Valley limestone deposits, camera facing south. Mountain Quarries of the Pacific Portland Cement Company in the foreground, quarry of the California Rock and Gravel Company in middle-ground. Cave Valley and adjacent gulches are roughly aligned parallel to the regional structure which is slightly north of west.|
|Geologic Map of the Cool-Cave Valley Area Showing Location of Limestone Deposits. (The limestone deposits mapped are: 1. Auburn, 2. Brown’s Bar, 3. Buckeye Canyon, 4. Burton, 5. Cool-Cave Valley, 6. Cowell, 7. DeWitt, 8. Hotaling, 9. Lime Rock, 10. West Cool-Cave Valley, 11. Long Point, 12. Muegge, 13. Pacific Portland Cement, 14. Rattlesnake Bridge, and 15. Spreckels.|
The following information is taken from "Table 1. Limestone deposits in the general area of the Cool-Cave Valley limestone," (circa 1954) on pages 462 and 463:
(No. on map, Plate 3) 5; (Deposit) Cool-Cave Valley; (Owner) North ¼ owned by Pacific Portland Cement Company, 417 Montgomery Street, San Francisco. South ¾ owned by Henry Cowell Lime and Cement Company, 2 Market Street, San Francisco; (Location) Secs. 6, 7, 18, T. 12 N., R. 9 E., M.D.; (References) Hanks 84:107; Crawford 94:391-392; Lindgren 94:3; Crawford 96:628; Aubury 02:17; 06:68; Tucker 19:304, 390-391; Logan 21:431-432; 24:8; Young 25:13-16; Logan 26:442, 443; 27:282; Laizure 27:208; 29:251; Logan 38:277, 280; 47:222, 224-226, 232-233; Bowen and Crippen 48:73, 80.
"The Cool-Cave Valley limestone deposit consists of two elongate lenses extending in northerly direction through the Sierran foothills about 4 miles east of Auburn, California. Limestone has been quarried from both lenses. Mountain Quarries, at the north end of the deposit, was one of the chief sources of limestone in northern California from 1910 to 1930. The California Rock and Gravel Company now (circa 1954) operates a quarry for the production of limestone for use in sugar refineries in the central portion of the deposit adjacent to the idle Mountain Quarries.
"The geologic structure of the area has a north to northwest trend. In the area immediately surrounding the limestone, the rock is composed dynamothermally metamorphosed fine-grained basic volcanic rocks commonly called greenstone, of undetermined age. To the west and north of the limestone are extensive beds of Carboniferous metamorphosed marine sediments and masses of amphibolite. Both the limestone and the volcanic rocks are cut by dikes of medium-grained quartz diorite and diorite porphyry. The exact relationship of the limestone with the other rocks of the area is not clear.
"At Mountain Quarries, limestone was quarried by the glory hole method. from the quarry it was trammed through an adit to the crushing plant. Most of the stone was then shipped via railroad to the Pacific Portland Cement Company plant. After 1930 production was largely used in beet sugar refineries. Peak production varied from 1200 to 1500 tons per day.
"Since 1946, the California Rock and Gravel Company has operated a quarry in the central portion of the deposit. The 'coyote hole' method of quarrying is employed, whereby an entire year's production of 150,000 tons is dislodged in one blast. The rock is then run through a crusher and a sizing plant. Coarser sizes are shipped via railroad to beet sugar refineries while the finer material is trucked to a lime plant near Rattlesnake Bridge or sold as road metal. Estimated reserves of the entire deposit are 18,225,000 tons per 100 feet of depth.
"Approximately 4 miles east of Auburn, California is the Cool-Cave Valley limestone deposit. the deposit consists of two elongate limestone lenses extending from a point half a mile north of the town of Cool, El Dorado County, north for a distance of approximately 1 ¾ miles to just north of the Middle Fork of the American River in Placer County. The two lenses lie in secs. 6 and 7, T. 12 N., R. 9 E., M.D.M. The bulk of the deposit is in El Dorado County.
"The Cool-Cave Valley area is traversed by State Highway 49 which crosses the south end of the deposit. Dirt roads branching off Highway 49 give access to nearly all parts of the limestone deposit. The nearest railroad is the main line of the Southern Pacific which runs through Auburn in a northeasterly direction. Until 1942, Mountain Quarries of the Pacific Portland Cement Company at the north end of the deposit on the Middle Fork of the American River, was served by a company-owned railroad which connected with the Southern Pacific at Auburn. The old railroad right-of-way is now a dirt road.
"Topography of the region is characterized by steep-walled canyons and moderately steep peaks. Elevations vary from 500 to 1800 feet. The topography and drainage pattern is partly controlled by the north to northwest trend of the major geologic structures. As the Sierra Nevada has been tilted in a general southwesterly direction, the main rivers and stream flow in that general direction, while the small tributaries tend to flow to the northwest or southeast in response to the structure.
|Figure 1. Ruins of old lime kiln at the south Cool-Cave Valley deposit on the east side of State Highway 49|
"Limestone has been quarried at both of the lenses. Lime was produced in the early history of the operations by burning the lime with wood in stone lime kilns. During the 1880's, the Cave Valley deposit was operated by the firm of Davis and Cowell (Hanks, 1884). In 1894 the Cave Valley Lime Company produced 150 to 160 tons of lime per month during the summer from two kilns which were located alongside of the Auburn-Cool road (Crawford, 1894). Ruins of these old kilns may be seen today north of Cool close to State Highway 49.
"In 1910 the Pacific Portland Cement Company opened its Mountain Quarries on the south side of the Middle Fork of the American River for the production of limestone for use in the company-owned cement plant in Solano County (Logan, 1947, p. 232). From 1910 until about 1930 this quarry was one of the chief sources of limestone for the cement, sugar, and steel industries in northern California. After 1930 production was smaller, the cement plant in Solano County having been idle part of the time. In 1942 the quarry was shut down, and the railroad and crushing plant were dismantled. Since that date, it has been idle.
"In 1946 the central portion of the northern lens. just south of Mountain Quarries, owned by the Henry Cowell Lime and Cement Company, 2 Market Street, San Francisco, was leased to the California Rock and Gravel Company, 1800 Hobart Building, San Francisco (Logan, 1947, p. 225). At the present time this firm operates a quarry at this site for the production of limestone, which is used chiefly in sugar refineries.
|Figure 2. Old limestone quarry in the south Cool-Cave Valley deposit; view north from State Highway 49.|
General Geology (of Cool-Cave Valley)
The general trend of the rock units is north to northwest. The rocks of the region consist of a series of dynamothermally metamorphosed marine sediments of the Calaveras group and metavolcanic rocks, some of which probably belong to the Calaveras group and some of which probably do not.
"The Calaveras group, of which the limestone has been considered as part, makes up the bulk of the Paleozoic part of the bedrock of the Sierra Nevada. For a long time the Calaveras group was considered to be Carboniferous in age; however, recent work has caused a number of investigators to believe that it includes a greater part of the Paleozoic section than just the Carboniferous (Taliaferro, 1943, p. 280). Stratigraphic relations of the limestone with other members of the Calaveras group are not clear in many areas.
Rock Units (of Cool-Cave Valley)
"Metavolcanic Rocks. In the immediate area of the Cool-Cave Valley limestone, the enclosing rock consists chiefly of metamorphosed volcanic rocks, green schist and massive unlaminated greenstone being the most abundant. Moderately resistant as compared with the other rocks of the region, the greenstone occurs in bold massive outcrops. Massive blocky greenstone is most common east of the Cool-Cave Valley limestone whereas green schist is common to the west. Green schist is well exposed in road cuts in the vicinity of the State Highway 49 bridge over the Middle Fork of the American River.
"Where fresh, the massive greenstone is dull green to greenish-brown while the green schist is brilliant green. Both weather readily, first to a dull red or brown and then to a red soil.
"The greenstone and green schist have apparently derived from a series of fine-grained basic volcanic rocks, many of them tuffaceous. They are composed chiefly of chlorite with varying amounts of epidote, actinolite-tremolite, plagioclase, hornblende, zoisite, and small amounts of iron oxide and pyrite. Calcite is sometimes present in veinlets and cavities. Prophyroblastic textures are common.
"Amphibolite. Two miles west of the Cool-Cave Valley limestone is a 2000-foot-wide bed of hornblende-plagioclase amphibolite. It is massive to schistose and varies from a light-colored plagioclase-rich variety to a dark-green variety composed chiefly of hornblende.
"Cutting across the limestone in the north end of Mountain Quarries at a small angle to the elongation of the lens is a 45-foot wide dikelike mass of dark grayish-green rock containing numerous amygdules of white calcite. It is badly-sheared porphyritic amygdaloidal basalt composed of calcite amygdules and pseudomorphs of intermeshed calcite and relict plagioclase set in a dark fine-grained groundmass of chlorite and iron oxide.
"Diorite Porphyry. Both the limestone and the metavolcanic rocks in the vicinity of the limestone have been intruded by a number of diorite porphyry and quartz diorite porphyry dikes. they cut the limestone and metavolcanic rocks at small-angles both in dip and strike. The dikes are light to medium gray in color and are composed of phenocrysts of plagioclase, epidote, chlorite and iron oxide. Quartz may or may not be present. Much secondary calcite and usually small amounts of pyrite are present.
"Serpentine. Serpentine is widely distributed throughout the area. the largest serpentine body in this region crops out for about 1500 feet along an old railroad right-of-way on Robie Point in eastern Auburn. It is derived from basic intrusive rock, both the olivine and pyroxene have been altered to light and dark serpentine. There are many small serpentine bodies in the vicinity of the limestone, which have been altered to light iron oxide-stained talc.
"Metasedimentary Rocks. Metasedimentary rocks of the region include slate, chert, sheared sandstone and conglomerate, and limestone. All of the metasediments in the general area of the Cool-Cave Valley deposit have been considered to be part of the Calaveras group by Lindgren (1894). The Clipper Gap formation, part of the Calaveras group named by Lindgren, crops out in the southwestern portion of the adjoining Colfax quadrangle and is an extension of the series of metasediments in this area.
"Chert in this area varies from light to dark gray in color and is in places stained black with manganese oxide. The chert occurs in thin lenticular beds that are often contorted near the surface. Slate occurs in irregular beds and varies from a grayish cherty variety to a nearly black clayish variety. Also present in appreciable amounts are argillaceous sandstone, arkosic sandstone and fine- to coarse-grained conglomerate, all of which have undergone varying degrees of shearing.
"A wide belt of these metasediments are exposed along the Southern Pacific Railroad 3 miles to the north of the Cool-Cave Valley limestone deposit. A branch of this belt extends south to just east of the State Highway 49 bridge over the Middle Fork of the American River about one mile west of the limestone. Another wide belt of metasediments, which joins those to the north, extends in a general northwest direction about 2 miles east of the limestone.