The quicksilver resources of California . casing abovedescribed, then a much softer zone of somewhat decomposedserpentine, and then the hanging-wall serpentine. [See Fig. 41.] SONOMA COUNTY. Ill The ore forms in irregular lenticular bodies, more persistentvertically than horizontall3\ [See Fig. 42.] The ledge filling is generally a very hard crystalline rock,fissured and cross-fissured in all directions, and recemented bysubsequent depositions. The ore forms principallj in relativelj^softer zones in this material. It carries less iron pj-rites in thelower levels than at the surface, and the ex
The quicksilver resources of California . casing abovedescribed, then a much softer zone of somewhat decomposedserpentine, and then the hanging-wall serpentine. [See Fig. 41.] SONOMA COUNTY. Ill The ore forms in irregular lenticular bodies, more persistentvertically than horizontall3\ [See Fig. 42.] The ledge filling is generally a very hard crystalline rock,fissured and cross-fissured in all directions, and recemented bysubsequent depositions. The ore forms principallj in relativelj^softer zones in this material. It carries less iron pj-rites in thelower levels than at the surface, and the exudations of sulpho-salts are also much less in the lower levels, rendering theventilation of the mine a relatively easy matter. In the ledgefilling are found bunches of soft, whitish, somewhat unctuousmaterial—a decomposition product. It is impossible, due tothe complete decomposition, to determine the character of theoriginal material. The material, locally called caliche, issometimes barren, and sometimes carries sensible amounts of. Fig. 42. Great Eastern Mine—Plau showing the form of the ore bodies. cinnabar, but its presence generally indicates the proximity ofcinnabar deposits. On the 580-foot level an exposure of thecrjstalline fissured rock carrying cinnabar shows that some ofthese fissures are rather wide, over an eighth of an inch, andthat the rock is recemented by quartz containing no signs ofcinnabar. Clearly, then, this recementation took place subse-quent to the cinnabar deposition. The absence of gangue, the hard siliceous material on thehanging wall, and the character of the vein filling, all indicatea very strong silicification (cementation) process, but of anentirely different nature from that forming the chalcedonite quicksilver rock so often associated with cinnabar the levels above the collar of the shaft in the surface crop-pings some opaline rock is found, and the silicification (cemen- 112 QUICKSILVER RESOURCES OF CALIFORNIA. tationj of t
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectminesandmineralresou
