Annual report of the State Mineralogist for the year ending ... . are rich for a foot ortwo. The horse is always a portion of the hanging wall. No veins branchinto the foot wall. The width of the vein varies greatly, the greatestwidth being nineteen feet. A specimen of diabase from the 950-foot level(407), and two hundred feet from the slates, shows a great alteration,many of the augite crystals being reduced to chlorite. At the edge ofthe dike, adjoining the vein, the decomposition is more complete. Butsometimes two feet away the influence of vein-forming agencies uponthe crystalline rock is
Annual report of the State Mineralogist for the year ending ... . are rich for a foot ortwo. The horse is always a portion of the hanging wall. No veins branchinto the foot wall. The width of the vein varies greatly, the greatestwidth being nineteen feet. A specimen of diabase from the 950-foot level(407), and two hundred feet from the slates, shows a great alteration,many of the augite crystals being reduced to chlorite. At the edge ofthe dike, adjoining the vein, the decomposition is more complete. Butsometimes two feet away the influence of vein-forming agencies uponthe crystalline rock is not noticeable. East of Jackson the slatescontinue for nearly a mile. They are often pyritiferous (408), but notfissile, and evenly laminated, as are the black slates, in which the mainvein of the lode lies. A number of small veins occur which are indicated, more often, by aline of broken slates and a gouge-like appearance than by any largebodies of quartz. Near the town the slates strike but little west of north. GEOLOGY OF THE MOTHER LODE REGION. 71 Fig. 2 8. One mile east they vary to north 64 degrees west, then they becomemore siliceous and are greatly contorted, and often finely banded (409).The strike finally varies to north 80 degrees east. This is followed by aquartzite, and two miles east the rock becomes a chloritic schist; graniteoutcrops four miles east of Jackson Creek, five or six hundredfeet west of town, is an irregular dikeof diabase. It is not continuous, butdetached masses, more or less in line,have broken through the slates, dis-turbing and metamorphosing some distance down the creek therock is bedded and sometimes quiteslaty. The strike varies from north15 degrees west to north 35 degreeswest, with the dip 82 degrees of this rock present that pe-culiar fragmental appearance before noticed along the edge of the diabase: i^CTH- iSJ\/\ \\angular siliceous fragments imbedded */7^S{^^\\%^v^in a chloritic matrix (410), which
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Keywords: ., bookcentury1800, booksubjectgeology, booksubjectminesandmineralr
