By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Total recorded gold production for Napa County is 23,225 ounces, all from the Calistoga district in the northwest corner of the county. The first gold production recorded was in 1875 when $93,000 in combined gold and silver was listed (Davis, 1948, p. 165). Intermittent production continued to 1941.
Gold has been a byproduct from the Palisade and Silverado silver mines (Davis, 1948, p. 183). No other information on this district could be found.
Along the eastern border of the county is a 4-mile-wide belt of folded siltstones, sandstones, and a few limestones composing the Shasta Series, of Cretaceous age (Davis, 1948, p. 162). These rocks are flanked on the west by a 1/2-mile-wide strip of the Jurassic Knoxville Formation, which is the lower, conglomeratic unit of the Shasta Series (Weaver, 1949, p. 21-22).
The remainder of the northern half of the county is underlain by metamorphic and cherty sedimentary rocks and associated basic intrusive rocks of the Franciscan Group, of Jurassic age. In the western part of the county, the east side of the Napa Valley is covered by a thick section of Pliocene volcanic rocks, and on the west side of the valley, the Shasta Series is overlain locally by Pliocene volcanic rocks.
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