California mines and minerals . he 700-foot level downward. The mill consistsof thirty 850-pound stamps, dropping seven to eight inches 100times per minute. The Thorpe is another property that, like theGwin, was a producer in early days. The ledge was discovered in the50s, when the surface ground was sluiced away in placering, and theore worked in an arrastra. Later, shortly after 1870, a ten-stampmill was erected, but the high cost of mining and milling in those 338 CALIFORNIA MINES AND MINERALS days left very little net returns, and the mine was closed down, toremain idle until 1894, when th
California mines and minerals . he 700-foot level downward. The mill consistsof thirty 850-pound stamps, dropping seven to eight inches 100times per minute. The Thorpe is another property that, like theGwin, was a producer in early days. The ledge was discovered in the50s, when the surface ground was sluiced away in placering, and theore worked in an arrastra. Later, shortly after 1870, a ten-stampmill was erected, but the high cost of mining and milling in those 338 CALIFORNIA MINES AND MINERALS days left very little net returns, and the mine was closed down, toremain idle until 1894, when the present developments were com-menced. The Demorest Mine is situated about one and three-fourths milessouth-west of the Thorpe property, on the contact between the am-phibolite schists and Mariposa slate. The vein is strong, varying inwidth from four to twenty feet, and is somewhat of the character ofthe Gwin. The mine has been fairly well opened to the 400-footlevel by an inclined shaft, with a number of crosscuts and Thorpe Mine, Fourth Crossing. The ore is a bluish white quartz, rather ribbony, and carries three tofour per cent sulphurets. A five-stamp mill on the property servesto thoroughly test the ore-body. The entire plant is operated bysteam. The Lightner Mine, at Angels, is unique in being the first pro-ducing property in the county to be operated entirely by electricpower. Situated immediately north of the Utica, the ore-body is ofprecisely the same character, and, as at that mine, the total absenceof a waste dump is a peculiarly noticeable feature. The main shaftis vertical, 400 feet in depth, and has three compartments. The MINES OF CALAVERAS COUNTY 339 gallows frame is 104 feet high, and contains the ore bins and rockbreaker. The mill has forty 850-pound stamps, making 105 dropsper minute. Five tons per stamp per day are crushed through No. 1tin screens. The sulphurets are saved by fifteen four-foot and sixsix-foot Frue concentrators, giving clean concen
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