Location and History
The Piru district is in northeastern Ventura County in the vicinity of the creek of the same name. The Frazier Mountain district is just to the north, and the town of Gorman on the Ridge Route highway is 10 miles to the northeast. Placer mining was begun here in 1841 by Andrew Castillero, and gold from the district was shipped to the U.S. Mint in Philadelphia in 1842. Small-scale placer mining continued intermittently through the 1890s, and there was some work again in the 1920s and 1930s. Among lode-gold mines, the principal operation was the Castac mine, which has an estimated total output valued at about $160,000.
Geology and Ore Deposits
The placer deposits are in and adjacent to the upper part of Piru Creek, chiefly in the vicinity of its junction with Lockwood Creek and to the east in the Gold Hill area. The gold has been recovered both from Recent stream gravels and older terrace deposits on the hills north of the Creek. The placer gold often is coarse-grained. There are a number of north-striking gold-quartz veins that range from a few inches to about 4 feet in thickness. The veins occur in shear zones and usually in granitic gneiss or hornblende schist. The ore contains free gold and varying amounts of pyrite. Milling ore sometimes averaged 1/2 ounce of gold per ton.
Bowers, Stephan, 1888, Gold-Ventura County: California Min. Bur. Rept. 8, pp. 680-684.
Huguenin, Emile, 1919, Gold-Ventura County: California Min. Bur. Rept. 15, pp. 759-760.
Tucker, W. B., 1925, Gold-Ventura County: California Min. Bur. Rept. 21, pp. 229-232.