Bulletin . n 360 feet (bar.). Production ofquicksilver began here with an output of 412 fiasks in 1875; and themine is credited with a total output to date of 42,092 flasks, or nearlytwo-thirds of the total output of Sonoma County to the end of 1917. ^See p. 217, i)ost. 188 CALIFORNIA STATE MINING BUREAU. This includes the yield of the Mt. Jackson mine adjoining, as the twowere operated in conjunction for a number of years, and their individ-ual figures are not separable. As noted in a foregoing paragraph,from 1882 to 1894, the Great Eastern mine was the only quicksilverproducer in Sonoma Coun
Bulletin . n 360 feet (bar.). Production ofquicksilver began here with an output of 412 fiasks in 1875; and themine is credited with a total output to date of 42,092 flasks, or nearlytwo-thirds of the total output of Sonoma County to the end of 1917. ^See p. 217, i)ost. 188 CALIFORNIA STATE MINING BUREAU. This includes the yield of the Mt. Jackson mine adjoining, as the twowere operated in conjunction for a number of years, and their individ-ual figures are not separable. As noted in a foregoing paragraph,from 1882 to 1894, the Great Eastern mine was the only quicksilverproducer in Sonoma Count3^ This Great Eastern-Mt. Jackson lode is peculiar because of its isola-tion from other workable quicksilver deposits and from any knowneruptives. It resembles somewhat the Culver-Baer ledge with its bold,ochreous outcrop between a serpentine hanging-wall and sandstonefootwall. (Seen at left of Photo No. 38.) The strike is north of westand dips north at 50° to 60°, being steeper at the surface. The Great. Photo No. 38. Great Eastern Mine, near Guerneville, Sonoma County. Ledge outcrop atleft; furnaces in center; furnace dump at right. Eastern vertical shaft sunk in the sandstone footwall is down 550,with two winzes of 160 each sunk from the 500 level. There is alsoa 400 drift on the 500 level. The collar of the shaft is about 200below the upper outcrop, and at that level there is a tunnel in 1100,with connecting drifts and stopes in the ledge above. From the shaftthere are levels at 150, 220, 360 and 500, respectively. The ore shoot is enclosed within the ledge of opalized rock which wasoriginally probably mostly serpentine. Becker^ considers that thissilicification preceded the deposition of ore, though somewhat closelyconnected with it. Occasionally a little pyrite accompanies the cin-nabar. The ledge filling is characterized by numerous cross-fissures,at a flat angle, filled with quartz stringers, like the ladder veinsdescribed by The ore forms principally in r
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