392 H. W. TURNER — GEOLOGY OF MOUNT DIABLO. 



Cinnabar occurs here, at the contact of the audesite with the adjacent 

 unaltered shale. It is associated with chalcopyrite and calcite, some of the 

 cinnabar being so intermingled with the calcite as to indicate contemporaneous 

 deposition. There is no quartz at this place. Solfataric action is still going 

 on in the old tunnel run in for cinnabar. 



At a point about one mile south of the main peak there is a vein of quartz, 

 much stained by ferric oxide. In samples of this, Dr. Melville found cin- 

 nabar in considerable quautity. 



Coal. — Extensive beds of coal occur in strata of Tejon age, about five 

 miles northeast of the main peak. These deposits have been successfully 

 rained for many years. The coal is rather friable, and inferior to that of 

 Bellingham bay and other more northern localities. On the dumps of some 

 of the old mines (Black Diamond and others) there are abundant pieces of 

 carbonized wood, usually containing pyrite. 



There are also some coal seams, that will sooner or later be worked, about 

 two and a half miles southwest of the main peak, by Pine creek, in strata of 

 the Tejon, which is the usual coal-bearing formation of central California- 

 Coal of a poor quality is obtained, however, from nearly horizontal beds of 

 Pliocene age, at lone, Amador county, California, and at some other points. 



Numerous coal seams occur in the neighborhood of Corral hollow pass, 

 southeast of Livermore. The strata are considerably faulted, and in conse- 

 quence the miners find difficulty in following the coal seams. The seams dip 

 at a high angle, and the coal is sometimes decomposed to a depth of fifty or 

 more feet by the action of surface waters, the resulting material being a rust- 

 colored spongy mass, which no one not familiar with coal prospecting would 

 suppose to indicate the presence of coal seams. 



According to Mr. J. Richards, who kindly showed me about the mines, the 

 coal above water-level contains much gypsum, but below the water line the 

 sulphate of lime is in solution in the water and the coal is in consequence of 

 better quality. I myself noted some gypsum in the coal. At the time of 

 my visit (1886) there were no producing mines, but the coal seams w^ere well 

 exposed at the Livermore, Richards and Coleman mines. At the latter 

 mine there was exposed a vein about five feet thick, dipping 80° north- 

 westward. Stratigraphically above the coal seam, in a shaly stratum, were 

 numerous oyster shells. 



In the Richards coal mine the coal seam, where observed, dips 35° north- 

 westward, and the coal was decomposed down eighty feet, following the vein. 



On the surface near the Richards mine, in sandstone, I collected Tejon 

 fossils (Turritella,uvasana, and others). 



At the present time (1890) some of these coal deposits are worked. 



Mineral Springs. — Besides the springs referred to in connection with the 

 quicksilver mine, mineral waters issue at several points. A warm spring 

 which I have not seen is said to exist in Mitchell cailon. 



