404 GEOLOGY OF THE EUREKA DISTRICT. 



PLATE VII. 



1. PHENOCRTSTS OF BLACK BORDERKD HORNBLENDE AND PLAGIOCLASE FELDSPAR IN HORNBLENDE- 

 HEARING PYROXENE-ANDESITE. 



Thiu section 77, magnified 50 diameters. The glass inclusions in the feldspars and the feldspar mioro- 

 lites in the groundmass are shown. 



2. BASALT. 



Thin section 257, magnified 225 diameters. The lath-shaped plagioclase and magnetite grains are dis- 

 tinctly shown, but the augite is not well defined. 



