By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Gold was mined in Los Angeles County - long before James Marshall's discovery in El Dorado County in 1848 - by Spaniards and Mexicans who worked placers 35 miles northwest of Los Angeles from 1834 to 1838. During the rush to California many prospectors settled in the Los Angeles area, where in 1857-58 more than 6,000 people were mining gold (Gay and Hoffman, 1954, p. 493).
Most of the production from the county was from lode deposits, although the San Gabriel district produced considerable placer gold. Gay and Hoffman (1954, p. 497) reported total county gold production at more than $24 million (about 109,200 ounces). From 1957 through 1959 gold mining was restricted to small yields from itinerant sand-and-gravel operations.
Gold has been mined at many places in the county. Some of the larger producers are the Acton and Neenach lode districts, the Bouquet and Texas Canyon placer districts, and lode and placer districts in the San Gabriel Mountains near Mount Baldy and in eastern San Gabriel Canyon. More than half the county production from 1880 through 1953 came from the Governor lode near Acton (Gay and Hoffman, 1954, p. 497).
The Acton (Cedar and Mount Gleason) district, in north-central Los Angeles County, produced at least 50,000 ounces of gold during 1880-1959, all attributed to lode mines, the most important of which was the Governor mine.
Pyritiferous gold-bearing veins occupy faults and zones of fractures in basic intrusives and metamorphic rocks of the Pelona Schist (age unknown) and in the San Gabriel Complex of Precambrian(?) age (Gay and Hoffman, 1954, p. 494).
ANTELOPE VALLEY DISTRICT
The Antelope Valley district is in northwest Los Angeles County, south of Neenach, along the Kern County line.
Gold was discovered in this area in 1934, and a small rush immediately followed. Although many claims were staked and many pits were dug, only the group of claims controlled by the Rivera Mining Co. was successful. Most of the mining was done during the first few years, and by 1946 all properties were idle (Wiese, 1950, p. 47). Total production was about 9,700 ounces of gold.
The country rock in the vicinity of the gold deposits is quartz monzonite of Jurassic (?) age. It contains large inclusions of limestone, hornfels, and quartzite, which are remnants of a metasedimentary sequence tentatively regarded to be of Paleozoic age (Wiese, 1950, p. 18-19).
The ore deposits are in quartz veins along the contact between the quartz monzonite and metasedimentary rocks. The gold occurs free in the quartz or is associated with sulfides that are present in small amounts (Wiese, 1950, p. 47).
SAN GABRIEL DISTRICT
The San Gabriel district, in east-central Los Angeles County, has produced both placer and lode gold. The San Gabriel River area has been worked intermittently for placer gold since 1848, but no production was reported for 1957-59. Before 1874, more than $2 million worth of placer gold (about 100,000 ounces) was mined; since 1880, about 20,000 ounces was mined. The lodes are credited with 50,000 ounces of gold (Gay and Hoffman, 1954, p. 495-496), most of which was probably mined before 1880. Total production for the district was about 165,000 ounces.
The lode deposits consist of gold-quartz veins that cut metamorphosed igneous and other metamorphosed rocks of the San Gabriel complex (Gay and Hoffman, 1954, p. 495). The veins are narrow and discontinuous, and the ore shoots are irregularly distributed.
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