The Los Burros district is in southwestern Monterey County in the Santa Lucia Mountains. It is about 80 miles south of Monterey and four miles east of Cape San Martin.
It is believed that this region was first prospected for placer gold and quicksilver in the early 1850s. Prospecting became so popular here that the Los Burros mining district was organized in 1875. In 1887 lode gold was discovered by W. D. Cruikshank at what is now the Buclimo mine. There was considerable excitement during the following few years, and a vast number of claims were located. The principal settlement was the town of Manchester or Mansfield, which burned down in 1892.
Another flurry of activity in the early 1900s followed placer gold discoveries in the various forks of Willow Creek. Intermittent small-scale prospecting and development work have continued in the district until the present time. There was a recorded production of several hundred dollars worth of gold in 1953 and again in 1963. It is believed that 2000 or more claims have been located in the district. The value of the total output is estimated to be about $150,000.
Geology and Ore Deposits
The Los Burros district is underlain by various rocks of the Franciscan F ormation (Upper Jurassic). Dark sandstone is most abundant and is also the chief host rock of the gold-bearing deposits. Also present are chert, shale, serpentine, and volcanic rocks. These rocks have been strongly faulted and sheared and locally metamorphosed. Numerous narrow northeast-trending veins, composed of quartz and small amounts of calcite, occur in shear and fracture zones and commonly with fault gouge.
Most of the gold has been recovered from small lenticular ore shoots in oxidized zones near the surface. The sulfides, which consist of fine-grained pyrite and small amounts of chalcopyrite and arsenopyrite generally, are low in gold content. Most of the placer gold has come from Willow Creek, and much of it was concentrated as coarse ragged fragments. Very small amounts have been found in Alder, Plaskett, and Salmon Creeks.
Ancona, Buclimo $62,000, Bushnell, Gorda, Grizzly, Mariposa, Melville, New York, Plaskett, Plaskett (placer) $18,000, Spruce (placer) $22,000.
Hart, E. W., 1966, Monte,ey County, gold: California Div. Mines and Geology County Rept. 5, pp. 44--52.
Hill, J. M., 1923, The Los Burros district: U. S. Geol. Survey Bull. 735-J, pp. 323-329.
Irelan, William, Jr., 1888, Los Burros district: California Min. Bur. Rept. 8, pp. 405-410.
Laizure, C. McK., 1925, Monterey County, Los Burros district: California Min. Bur. Rept. 21, pp. 37-41.
Mining and Scientific Press, vol. 104, pp. 696-698, May 18, 1912. Preston, E_ B., 1892, Los Burros district: California Min. Bur. Rept. 11, pp. 259-262.
Waring, C. A., and Bradley, W. W., 1919, Monterey County, Los Burros mining district: California Min. Bur. Rept. 15, pp. 602-605.