Abstract The discovery of the McLaughlin hot-spring type gold deposit in the old Knoxville mercury district sparked considerable interest and research into the origin and relation of mercury and epithermal gold mineralization in the California Coast Ranges Province. Silica-carbonate mercury mineralization occurs throughout the Coast Ranges, from Santa Barbara County in the south to Lake and Colusa counties in the north (Fig. 1). Since their discovery in the mid 1800’s California’s Coast Ranges mercury deposits have produced over 50% of the total production for the United States, and two of the mines, the New Almaden mine in Santa Clara County and the New Idria mine in San Benito County, rank as the fifth and sixth largest producing deposits in the world respectively (Bailey and others 1973). Prior to the discovery of the McLaughlin gold deposit in 1978, lode gold production from the Coast Ranges was very minor with an estimated total of about $750,000, with two thirds of this production from the Palisade and Silverado mines in the Calistoga silver-gold district (Clark, 1976). Notable quantities of lode gold have been produced from only two other areas; the Los Burros district in south western Monterey County where mesothermal gold-bearing quartz veins occur in Franciscan Complex rocks; and, from the Knoxville and Sulfur Creek mercury mining districts where gold was produced as a byproduct. The McLaughlin and Cherry Hill epithermal gold deposits (Fig. 1) were subsequently discovered in the Knoxville and Sulfur Creek mining districts respectively. Current reserves at the McLaughlin mine are