The quicksilver resources of California . ns mainly in serpentine material; at 300 feet it cuts across a veinhaving a nearly east and west strike; an understope, 20 feetdeep and 70 feet long, shows that the ore body lies in hardenedcontact mudrock. A shaft 80 feet deep shows that thebasalt lies here north of the mudrock, while in the uppertunnel it lies south thereof. The stope [see cross-section,Fig. 28] showed good ore, metacinnabarite, and some nativemercury in pockets next to the basalt. When the stopereached the understoping in the lower tunnel, it was shownthat the lower vein had a cross
The quicksilver resources of California . ns mainly in serpentine material; at 300 feet it cuts across a veinhaving a nearly east and west strike; an understope, 20 feetdeep and 70 feet long, shows that the ore body lies in hardenedcontact mudrock. A shaft 80 feet deep shows that thebasalt lies here north of the mudrock, while in the uppertunnel it lies south thereof. The stope [see cross-section,Fig. 28] showed good ore, metacinnabarite, and some nativemercury in pockets next to the basalt. When the stopereached the understoping in the lower tunnel, it was shownthat the lower vein had a cross strike to that on which thevein understoping was done, and the latter was never foundbelow. At the northwest end of the property is the knoll of whichsection 3 gives a cross-section. Several small pockets of orewere found in the tufa overlying the top. The tunnel (/)cuts through the entire knoll, running for the greatest part inserpentine. Ore was only found in the basalt near thenorthern end. It forms in seams in the basalt. In some of. Fig. 28. Manhattan Mine—Section over the works at (/,). 88 QUICKSILVER RESOURCES OF CALIFORNIA. these seams the main filling is formed by bands of iron pyrite,with thin, intercalated seams of cinnabar; in others the fillingis opaline silica. The ore in the surface pockets carried alsoconsiderable iron pyrite. The hill is mainly serpentine andshale; the absence of basalt in the lower tunnel may be causedby a fault, the upper part of the basalt having slid northeastwith the slope of the hill. While the mine is not a great producer, it .s of great geologi-cal interest, because the relations between the igneous rocks,the countT} rock, and the ore deposits can be so well absence of ore deposits in the serpentine, even where it iscontiguous to the igneous rocks, must be noted. In oppositionto the ore occurrence in the Oathill mine, the ore deposits areall contiguous to the basalt and do not extend to an}- distancefrom it, except in the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectminesandmineralresou
