Gold Districts of California
Location. The Hornitos district is in the Sierra Nevada west gold belt in
western Mariposa County about 15 miles west of the town of Mariposa. The district contains
a several-mile wide belt of lode-gold mines that extends from the vicinity of the
Exchequer Reservoir south-southeast through Hornitos to the Indian Gulch area.
History. The streams in the area were first worked in 1849, and lode mining
began in 1850 at the Washington mine. The town was first settled by Mexicans who had been
driven out of nearby Quartzburg. The name Hornitos is a diminutive of "horno" or
small bake oven, from the Spanish. Mining activity was great from the 1860s through the
1880s, lesser from the 1890s to the 1920s. The Mt. Gaines mine was worked on a major scale
during the 1930s. Since World War II the area has been prospected, but there has been very
little recorded production. Historically, this is the most productive district of the
Sierra Nevada west gold belt.
Geology. The district is underlain by greenstone and greenschist in the west
portion and slate in the east. Also present are smaller amounts of amphibolite, mica
schist, and hornfels. A number of small granodiorite intrusions are exposed, along the
margins of which chiastolite-mica schist has developed.
Ore Deposits. A number of north-trending quartz veins and stringers containing
free gold and varying amounts of sulfides, chiefly pyrite, are present, as well as several
large bodies of mineralized greenstone or "gray ore". Some of the veins have
very flat dips. The ore shoots vary considerably in size with stoping lengths ranging from
a few to as much as 400 feet. Some of the veins have been mined to inclined depths of more
than 1500 feet. Milling-grade ore commonly contains from 1/3 to more than 1/2 ounce per
ton in gold.
Mines. Badger $80,000+, Doss $100,000, Duncan, Lost Douglas, Martinez, Mt.
Gaines $3.59 million, Numbers 1, 5, 8, and 9, Ruth Pierce $600,000, Washington $2,377,000.
Excerpt from: Gold Districts of California, by: W.B. Clark, California
Department of Conservation, Division of Mines and Geology, Bulletin 193, 1970.
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