This study was initiated to investigate the occurrence of cinnabar in the oxidation zones of some mercury sulfide deposits. Seven mines or mine districts were visited and samples were taken from both the oxidation and primary zones of these deposits in order to compare their mineralogies and assess the chemical changes that took place during oxidation. As a result of the study of these specimens, several limiting factors are suggested for the chemical environments and processes active in both the deposition and oxidation of mercury sulfide deposits.
Mt. Jackson Mines Guerneviile, California
The Mt. Jackson mine is a cinnabar deposit at the intersection of several faults with a serpentinite “sill” in Franciscan sandstones and shales. Footwall silica-carbonate rock consists of magnesite, quartz, and chalcedony, with accessory chromite, kaolinite, pyrite and millerite, and is cut by magnesite, dolomite, and quartz veins. Cinnabar occurs in these veins and as disseminations in the silica-carbonate rock. Bravoite and vaesite occur in some quartz-cinnabar veins.
The deposit is typical of many mercury deposits in serpentinite. It appears that serpentinite containing Ni, Fe, Mn and Al, when exposed to a solution of the composition of geologically related thermal springs can reasonably produce the silica-carbonate rock, veins and