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262 G. H. Williams—Pyrowene and Hornblende. 
is especially apparent. These must serve as types of all the | 
rest eM 
One rock from the locality just mentioned consists of an 
exceedingly fine-grained, jet black mass in which occasional — 
ronze-colored crystals of hypersthene are easily visible to the 
unaided eye. The microscope shows the groundmass to } 
composed essentially of small oval grains of brown hornblende 
with here and there a similarly shaped crystal of hypersthene 
or plagioclase. The large porphyritic crystals of hypersthene — 
unaltered. The hypersthene core is surrounded b a zone of 
perfectly compact brown hornblende whose external boundary, 
the section, except in a few spots, where, as already 
the characteristic inclusions remain, is covered with thee 
tongues and shreds of hornblende of a delicacy and tenulty 
