The quicksilver resources of California . in this mine form in the same serpentinewhich runs along the southwestern border of the mineralizedzone of the Manhattan mine. This belt extends for severalmiles to the southwest, but, except at its contact with the Neo-comian at Knoxville, does not contain a single ore body of anyconsequence. The mineralized zone of the Boston mine has anorthwest strike, and dips at about 45° to the northeast. Itscross-section is given in Fig. 24. In the Neocomian sandstone, about 1200 feet northeast of NAPA COUNTY. / / the ore zone, some work has been done, confirmin
The quicksilver resources of California . in this mine form in the same serpentinewhich runs along the southwestern border of the mineralizedzone of the Manhattan mine. This belt extends for severalmiles to the southwest, but, except at its contact with the Neo-comian at Knoxville, does not contain a single ore body of anyconsequence. The mineralized zone of the Boston mine has anorthwest strike, and dips at about 45° to the northeast. Itscross-section is given in Fig. 24. In the Neocomian sandstone, about 1200 feet northeast of NAPA COUNTY. / / the ore zone, some work has been done, confirming the factthat cinnabar forms in the sandstones; tests of the latter takenfrom various places indicate that cinnabar is disseminated allthrough this lormation. Combining this fact with the absenceof cinnabar in the serpentine, even when in close proximityto the igneous rocks in the Manhattan ground, and with thefact that in the Boston mine the workable ore bodies are inthe serpentine, the suggestion offers itself that the genesis of ore. PHOTO No. 5. BOSTON QUICKSILVER MINK. formation in this mine is similar to that in the ^tna mine—secondary concentration of the ore disseminated in the sand-stones connected in some way with the serpentine and igneousrocks. While, as far as known, no igneous rocks are presentin this mine, basalt is known to extrude within half a milefrom it, and it is very probable that intrusions of igneous rocksor laccolitic bodies may have influenced the concentration inconjunction with the serpentinization process. This supposi-tion finds confirmation in the fact that deposits from solfataricsprings can be traced from the Manhattan to the Boston mine. 78 QUICKSILVER RESOURCES OF CALIFORNIA. The intense chemical actions which have undoubtedly takenplace in this zone, and the great amount and variety of sulphurcompounds found therein, indicate undoubtedly close connec-tion with igneous actions, and can hardly be attributed exclu-sively to the reducing agen
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