Vol. 4] Knopf-Thclen. — Geology of Mineral King. 



253 



of highly sheared volcanic rock' intercalated between beds of 

 clay slates. The rock differs from the others of the region in 

 containing abundant triclinic feldspar and a weakly pleochroic 

 light green hornblende. Cataclastic phenomena are illustrated 

 in great abundance. The granulated remains of phenocrystic 

 quartz seem to be present, bu1 are not conclusively demonstrable. 

 The chief interest attaching to this rock is due to the peculiar 

 occurrence of tourmaline in it. The tourmaline was found occur- 

 ring as a peripheral fringe around a shattered feldspar, and 

 could be seen sending apophysal tongues into the core of the 

 phenocryst. 



The creek heading near the Empire Mine (N.E. of Mineral 

 King) crosses several hundred feet of altered volcanic rock. The 

 rock is of bluish gray color, fine grained, and shows but a rude 

 schistosity. Its most conspicuous feature is the abundance of 

 sheared streamers of ferromagnesian material, commonly re- 

 placed by epidote. Under the microscope some drawn-out ag- 

 gregates of intensely pleochroic basaltic hornblende can be seen 

 to have escaped the general alteration. Some large masses of 

 granular epidote surrounded by opaque earthy material occur in 

 considerable areal proportions. Cataclastic feldspars, too far 

 affected by decay to leave their exact nature determinable, are 

 present in no great abundance. The groundmass is cryptocrys- 

 talline. Broken apatite needles, and magnetite with associated 

 leucoxene, constitute the accessories. 



Large bodies of sheared andesite (PI. 29B) occur on Crystal 

 Creek at an altitude of 10,000 feet. Its color is a dark grayish 

 green, interspersed with numerous regular patches of flaky bio- 

 tite. These aggregates assume rectangular forms, uniformly 

 oriented, and suggest a derivative origin from former pheno- 

 crysts. In this section a very abundant generation of large 

 feldspar phenocrysts, affected by dynamic agencies and nearly 

 obliterated by kaolinization, becomes apparent between crossed 

 nicols. Some of the feldspar crystals still show evidence of their 

 triclinic character, and upon a favorable section a symmetric 

 extinction angle of 22° was obtained. Dark aggregates of flaky 

 biotite are common, but nothing can be discerned as to their 



