The Mother Lode region of California . Croppings of the Louisa Mine, Covlterville, Mariposa County. THE MOTHER LODE REGION—MARIPOSA COUNTY. 145 Pine Tree Mine.—This adjoins the Josephine, and is 3 miles north ofBear Valley. One of the old tunnels driven by the former operators hasbeen cleaned out and retimbered, and a hoisting engine set up under-ground about 600 feet from the mouth. Here a shaft has been sunk toa depth of 300 feet below the level. Ventilation is secured by an upraisethrough old workings above the hoist connecting with an upper engine is operated by steam carried in
The Mother Lode region of California . Croppings of the Louisa Mine, Covlterville, Mariposa County. THE MOTHER LODE REGION—MARIPOSA COUNTY. 145 Pine Tree Mine.—This adjoins the Josephine, and is 3 miles north ofBear Valley. One of the old tunnels driven by the former operators hasbeen cleaned out and retimbered, and a hoisting engine set up under-ground about 600 feet from the mouth. Here a shaft has been sunk toa depth of 300 feet below the level. Ventilation is secured by an upraisethrough old workings above the hoist connecting with an upper engine is operated by steam carried in from the boilers at the mouthof the tunnel, the exhaust passing out through the raise. Owing to thecareful manner in which the steam pipes have been packed, there islittle condensation in the pipes, and the temperature at the station is. not uncomfortably warm. In sinking the shaft, a very interesting faultwas discovered about 300 feet from the platform, the character of whichis illustrated in the accompanying drawing (Fig. 35). The indications are that the formation on the hanging-w^all side of thefault has slipped downward, and that if sinking were continued onthat portion it would be found to cut out, though in what distance it isimpossible to say. The foot-wall portion, however, will extend down-ward to indefinite depth. The shaft is being sunk through the heart ofthe ore-shoot opened by the old company, it being the purpose to ascer-tain as quickly as possible whether payable ore still remains in the10—MB 146 CALIFORNIA STATE MINING BUREAU. mine, and if so, how much. The Pine Tree Mine is everywhere char-acterized by its massiveness and its entire freedom from slaty inclusionsIron pyrite occurs in the quartz, but is not abundant. The vein isusually well defined by smooth walls, the foot-wall being alway
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