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Mariposa County

  • Mariposa County Limestone/Marble (circa 1905) - Excerpt from The Structural and Industrial Materials of California, Bulletin No. 38, California, State Mining Bureau, San Francisco, California, 1906.

    "A belt of crystalline limestone, some of which would make handsome structural and ornamental marble, occurs on the south side of the South Fork of Merced River, near Hite's Cove, where it is exposed on the grade road. No effort has ever been made to develop it."

  • Mariposa County Mines and Mineral Resources (circa 1913-1914) - Excerpt from Report XIV of the State Mineralogist - Mines and Mineral Resources of Portions of California, Chapters of State Mineralogist's Report - Biennial Period 1913-1914, Part IV. "The Counties of Fresno, Kern, Kings, Madera, Mariposa, Merced, San Joaquin, Stanislaus," by F. L. Lowell, Field Assistant (field work in July, 1914), San Francisco, California, July, 1915, California State Mining Bureau, San Francisco, California, 1916, pp. 173-370.

    "Mariposa County might be said to possess more distinctions than any other county in California from the fact that not only does the southern extremity of the famous 'Mother Lode' of the State end in this county but also that the famous Yosemite Valley and Mariposa Grove of Big Trees are included in it.

    "The county is bounded on the north by Tuolumne County, on the southeast by Madera County, and on the west and southwest by Merced County. The greater portion of the county is drained by the Merced River and its branches with the exception of that portion extending from the Mariposa Grant to the south end of the county. While the county receives a fair amount of rainfall, yet water is not very abundant during the summer and the power used in the prosperous days of mining in the county was derived from the then abundant wood fuel. Wood as a fuel at the present time is too expensive for working the grade of ores that now prevail (circa 1914).

    Power (in Mariposa County)

    "Some mines along the Merced River develop hydroelectric power from the river for their own use and the Mariposa Grant also supplies a limited amount of power for lighting purposes and mill power from its plant on the Merced River at Bagby. Their lines run from the Merced River through the grant to the towns of Mt. Bullion and the county seat, Mariposa. The plant consists of a flume 400 feet long by 16 feet wide and 6 feet deep which carries water under a 34-foot head to three Pelton wheels which are 27, 30 and 40 inches in diameter, respectively. The plant is capable of developing 600 horsepower and the power is generated by two Westinghouse dynamos.

    "The Pacific Gas and Electric power line comes from Tuolumne County to the Peñon Blanco mine and thence through the town of Colterville to the Potosi gold mine and owned by the Merced Gold Mining Company.

    "A company formerly had a power plant at Exchequer on the Merced River, but their plant was washed out during the heavy freshet of the winter of 1913. The San Joaquin Power and Light Company, which generates power from Merced Falls in Merced County, owns a power line which extends as far as the Mt. Gaines mine in the Hornitos mining district. This company also uses the Exchequer line for transmitting power.

    Mariposa Commercial and Mining Company's dam and hydroelectric plant on the Merced River at Bagby, Mariposa County, California. Mariposa Commercial and Mining Company's dam and hydroelectric plant

    Geology (of Mariposa County)

    "Mariposa County is about 65 miles long and 35 miles wide. The serpentine, amphibolite schists and metamorphic slate belt comes as far south as the Mariposa Grant and south of this estate the granites of the eastern portion of the county crowd over toward the west, thus ending the so-called 'Mother Lode.' The 'Grant' boundaries appear to be well chosen so far as including most of the Mother Lode vein south of the Merced River is concerned, for, outside of these boundaries, the veins are smaller.

    "In the southeastern section of the county there is a limestone belt with a northeast and southwest direction which extends for some distance through the county. This limestone belt carries copper in considerable quantities. The formation in the eastern part of the county which is taken up by the Yosemite National Park, is mostly of granite and heavily timbered. No mineral is reported and no prospecting is being done within the boundaries of the National Park.

    "Mariposa County had many producing mines at one time but many of the larger ones reached a zone of decreased values and ceased operations at this point. On the Mother Lode in other counties, this same lean zone has been encountered and, in some cases, it has been pierced and better values found below. This advanced prospecting has not been done to any extent in this county (circa 1914), and it remains to be proven whether the shoots go down. Some of the mines have very enviable reputations as producers from the surface down to the point of abandonment. The fuel question has been a drawback to the county of late years. There are ores that could be worked at a profit if cheap power could be had. Wood costs $2.50 to $4 per cord delivered."

    Granite (in Mariposa County)

    "Granite abounds in large quantities in Mariposa County of the same variety as the famous granite at Raymond in Madera County, but it is so far from transportation that it is not able to compete at present (circa 1914) with that more favorably situated. A granite property consisting of 50 acres of patented land located in Sec. 20, T. 6 S., R. 19 E., M.D.M., was located in 1906 by Guido Vignalo but was deeded to the State for taxes.

    "It is 15 miles by wagon road from Raymond and the granite is the same as that of the Raymond granite but is not be worked (circa 1914)."

  • Mariposa County Mineral Industry (circa 1919) - Excerpt from California Mineral Production for 1919, Bulletin No. 88, by Walter W. Bradley, California State Mining Bureau, 1920, pp. 153.

    Area: 1,463 square miles.
    Population: 2,775 (1920 census)
    Location: Most southerly of the Mother Lode counties. East-central portion of state.

    "Mariposa County is one of the distinctly 'mining' counties of the state, although it stands but thirtieth on the list of counties in regard to the value of its mineral output for 1919, with a total of $410,535, as compared with the 1918 figures of $352,504.

    "Its mineral resources are varied; among the most important items being barytes, copper, gems, gold, lead, marble, silver, slate, soapstone, and miscellaneous stone.

    "The Yosemite Valley is in Mariposa County.

    "Commercial production for 1919 was as follows:"

    (Headings for the information below are: Substance, Amount, and Value.)

    Copper, 24,879 lbs., $4,627
    Gold, ---, $400,200 (estimated)
    Silver, ---, $5,500 (estimated)
    Stone, miscellaneous, ---, $400
    Other minerals, ---, $8
    (Total value) $410,535

    Mariposa County, 1916 Map, from California Mineral Production for 1919 (with County Maps), Bulletin No. 88, by Walter W. Bradley, California State Mining Bureau, San Francisco: California State Printing Office, 1920, pp. 190. Mariposa County , 1916 Map
  • Mariposa County Limestone Industry and Deposits (through 1947) - Excerpt from “Limestone in California,” by Clarence A. Logan, California Journal of Mines and Geology, Vol. 43, No. 3, July 1947, California Division of Mines, San Francisco, California, pp. 175-357. Used with permission, California Department of Conservation, California Geological Survey.)

    "From 1927-44, limestone was quarried at Mariposa County for making portland cement at a plant near Merced. There is no other record of production. The Yosemite Valley Railroad which connected with two mainline railroads at Merced and followed the winding coarse of Merced River to El Portal, discontinued freight service, depriving the county of its only rail outlet. The long truck haul to outside points would be a handicap.

    "The Carboniferous (Mississippian ?) beds so rich in limestone in Tuolumne County extend southeastward through Mariposa County, but only the northwest part has been mapped in detail. The geologic map of this area shows only two lenses of limestone at and near Bower Cave. Other large deposits exist farther south and east at Briceburg, near Hite Cove, and at Jenkins Hill, the last being the only deposit so far worked."

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