Location and History
This district is in the northwest comer of Mariposa County, in the general area of Hunter Valley, the Don Pedro Reservoir and Lake McClure. It was named for William W. Hunter, a well-known engineer. There was extensive placer (Gold mining here during the 1850s and some copper mining in the 1860s. The lode gold mines were active until the early 1900s. Some mining was done again during the 1930s, and the Pyramid mine has been prospected recently.
Geology
The district is underlain by northwest-trending belts of slate of the Mariposa Formation (Upper Jurassic) and greenstones, chert and slate of the Amador Group (Middle to Upper Jurassic). Several small diorite and granodiorite intrusions are mapped.
Ore Deposits
A number of northwest-striking systems of gold-quartz veins are in the slate, chert and greenstone. Numerous stringers and cross veins are present. A number of high-grade pockets have been found. The ore contains free gold and often abundant sulfides, and milling ore commonly averaged one ounce per ton in gold. None of the veins have been mined to depths of more than a few hundred feet.
Mines
Blue Cloud, Cotton Creek, Iron Duke, Morning Star, Oak and Reese $500,000-$600,000, Orange Blossom, Pyramid $200,000, Choolllouse, Yellowstone.
Bibliography
Bowen, O.E., 1957, Mariposa County, Oaks and Reese and Pyramid mines: California Jour. Mines and Geology, vol. 53, pp. 145-147 and 158.
Castello, W.O., 1921, Mariposa County, Hunter Valley district: California Min. Bur. Rept. 17, pp. 94.-95.
Turner, H.W., and Ransome, F. lo, 1897, Sonora folio: U.S. Geol. Survey Geol. Altas of the U.S., folio 41, 7 pp.
