RSS FeedsMineral & Rock Resources
Former Homestake Mine, Napa County
Various mineral resources have been mined in Napa County. Mercury and mineral water were the most valuable mineral resources historically. Today, because of growing development, building stone and aggregate are the most valuable commodities.
This chapter describes in detail the mineral and rock resources in Napa County. Historically, various mineral resources have been mined in Napa County. The two most valuable mineral commodities in economic terms have historically been mercury, or quicksilver, and mineral water. More recently, building stone and aggregate have been the most economically valuable mineral commodities in the County. This reflects the growing need over recent decades for construction materials as the population of the region grows.
The principal regulatory document pertaining directly to mining and mining reclamation in California is the Surface Mining and Reclamation Act (SMARA) of 1975 (Chapter 9, Division 2, of the Public Resource Code). Napa County is the lead agency for implementing the requirements of SMARA. Special Report 146, prepared under the authority of SMARA, focused on classifying land in the San Francisco-Monterey Bay region, including Napa County, into mineral resource zones (MRZs) based on guidelines adopted by the California State Mining and Geology Board. Areas were zoned MRZs if they were identified as being within areas subject to urbanization. This classification project has been designed to assist and guide local lead agencies, such as Napa County, in preserving essential mineral resources for future use through proper zoning ordinances. Three principal MRZs were identified in Napa County, although MRZ maps were not prepared for the entire County.
There are currently four active mines (rock quarries) in Napa County, two of which are not presently being mined but only serve as mineral storage areas. These quarries produce construction materials. The only significant mine currently in operation in Napa County is Napa Quarry.
The principal constraints to future mining operations in Napa County relate to permitting, economics, the environment, and politics. The geologic opportunities for future mineral extraction in Napa County are not clearly known because the County has not been fully mapped for MRZ zones. However, the general geology of the County suggests that the potential for favorable aggregate rock does exist.
