Geological Notes on the Sierra Nevada. — Turner. 299 
deal of epidote in small grains and sometimes zoisite. These 
rocks resemble to a marked extent the greenstone schists of 
Michigan, so admirably described by professor G. II. Wil- 
liams/'* Large areas of amphibolite-schist are shown on the 
Sacramento. Placerville and Jackson atlas sheets. 
Copper. Copper is found in a belt of amphibolite-schist 
that lies just west of the Bear mountains in Calaveras county, 
and in the extension of this belt to the northwest into Eldo- 
rado county are frequent deposits of copper and iron sulphur- 
ets, which have been the source of a considerable copper 
industry. The* ore is said at Copperopolis and at Campo Seco 
to carry several dollars in gold to the ton. 
Amphibole-talc rocks. Hocks of this series occur as narrow 
streaks in the Paleozoic schists. They have been studied by 
the writer chiefly in the area of the Jackson sheet, where they 
appear to occur only in the Calaveras formation, chiefly in 
narrow streaks evidently representing basic dikes, for in 
places they contain cores of pyroxene altering to amphibole. 
This is usually colorless in thin sections and is probably tre- 
molite, but some of the amphibole corresponds more nearly to 
actinolite. Portions of the dikes are now altered to tale. 
Sometimes serpentine is associated with the amphibole and 
talc. In a dike three-quarters of a mile northeast of Oleta 
(No. 348 Amador county) the pyroxene is plainly altering to 
serpentine. The largest body of talc rock noted lies two and 
a half miles northeast of Angel's, in Calaveras county. In this 
case the area is rounded in shape anil about one-third of a 
mile in diameter. 
Diabase and Porphyrite. 
Rocks of the diabase series are very abundant in the Sierra 
Nevada. They occur as a rule associated with the auriferous 
slate series and in minor amount associated with granite. 
Much of the material classed as diabase lias been shown, on 
careful examination, to be fragmental and may be designated 
diabase-tuff, as the term is used by Rosenbusch. 
Some such areas were undoubtedly formed by eruptions 
which occurred at the time the sedimentary rocks now enclos- 
ing the tuff were being deposited : hut many of the fragmental 
diabase areas, or areas which arc in part fragmental, that scp- 
*Bull.U. s. Geol. Survev, No. 62. 
