128 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



A specimen from the dump of the Gold Hill mine consists of quartz 

 porphyry containing abundantly disseminated pyritohedral crystals 

 of pyrite. A large and completely sericitized phenocryst of feldspar 

 in this rock carries groups of slightly larger pyrite crystals of dom- 



10 

 Figs. 9-10. — 9, Pyrite. Highly modified crystal from Carroll-Driscoll mine, Boise County. 

 10, Pyrite. Dominantly cubic crystal from sericitized feldspar. Gold Hill mine, Boise 

 County 



inantly cubic habit with the modifying faces shown in Figure 10. 

 The forms and angles measured on one of these crystals are given in 

 the following table: 



Measurements of pyrite from Gold Hill mine 



