Gold Districts of California
LA PORTE
Location. This district is in southwestern Plumas County in the general vicinity
of the old mining town of La Porte, 25 miles south of Quincy and 50 miles northeast of
Oroville. It was one of the great placer-mining districts of the state.
History. The streams were placer-mined early in the gold rush and were reported
to have had very rich yields. The town, first known as Rabbit Creek, was renamed in 1857
after La Porte, Indiana. Hydraulic mining began in the middle 1850s and continued through
the 1880s. During this time the district was enormously productive; the output from 1855
to 1871 alone was reported to have been at least $60 million. Appreciable drift mining and
some lode mining were carried on. Some mining activity continued until the period of World
War I. The district was prospected again during the 1930s, but apparently little mining
has been done here since. La Porte was a noted early-day "snowshoe" or ski
resort.
Geology. The main Tertiary channel of the North Fork of the Yuba River, known as
the La Porte channel, extended south-southwest from Gibsonville into this district. From
here the channel continued southwest and south again to be joined by a branch from the
east from the St. Louis-Table Rock area. The main channel today continues on south to the
Poverty Hill and Brandy City districts. At La Porte, the channel is 500 to 1500 feet wide
and as much as 500 feet thick. The lower gravels are quartz-rich and up to 80 feet thick.
Most of the gold was recovered from near bedrock. The gravels are capped by thick beds of
sand and "pipe" clay. During the heyday of mining in the district, these lower
gravels yielded from 1/10 to as much as one ounce of gold per cubic yard. To the east the
channel deposits are capped by andesite as much as 800 feet thick. Also to the east,
considerable faulting has disturbed the channel gravels. Bedrock consists principally of
amphibolite, with a one-mile wide belt of slate and quartzite of the Calaveras Formation
(Carboniferous to Permian) in the central portion. There are some narrow gold-quartz veins
in the district.
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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