THE MINERALS OF IDAHO 153 



Specimens from the Independence mine consist of fibrous and 

 columnar masses of boulangerite associated with galena or with 

 pyrite in a quartz gangue. The boulangerite often has a felted or 

 curved-fibrous structure and specimens 5 to 6 inches through may 

 consist almost entirely of boulangerite. A sample of this material 

 upon analysis gave the following results: 



Analysis of boulangerite from Independence mine 

 Constituent Per cent 



Insoluble (quartz) 3. 58 



Lead (Pb) 53. 79 



Silver ( Ag) Trace. 



Iron (Fe) .41 



Antimony (Sb) 23. 83 



Arsenic (As) . 12 



Sulphur (S) 18. 11 



Total 99. 84 



In small open joints which cut the massive ore from this mine 

 rosettes of small crystals of boulangerite occur. They reach a 

 maximum length of about 1 millimeter and are highly polished with 

 metallic luster and light lead-gray color. They are all tabular 

 parallel to the front pinacoid a (100) and seem to possess a distinct 

 cleavage parallel to this plane. Several of these crystals were 

 measured on the 2-circle goniometer. 



These crystals are all simple in habit, the dominant forms, with 

 the orientation adopted, being the macropinacoid a.(100), the prism 

 n(\20) and the pyramid 2(124) while several other prismatic forms 

 occur as narrow faces, the form and habit of the crj^stals being as 

 illustrated in Figure 25. The prismatic zone is strongly striated 

 vertically. 



Since the angles did not seem to be in entire agreement with those 

 given for boulangerite, new axial ratios were calculated from the 

 measurements as follows: 



a = 0. 5038 log. a = 9. 70226 log. p = 10. 13386 p = 1.3620 



c= . 6862 log. c = 9. 83645 log. q = 9. 83645 q = . 6862 



The measured angles are compared with the angles calculated from 

 these constants as follows: 

 54347— 26t 11 



