382 Genth and Penfield — Contributions to Mineralogy. 



described. There were several, however, which deserve a 

 short notice. 



a. One variety in irregular flat particles between the cleavage 

 cracks of calcite or calcite and quartz, with a hackly fracture 

 and iron black color had the composition of nearly pure agui- 

 larite (a). 



b. A second variety made up of small capillary needle- and 

 wire-shaped individuals without any distinct planes, also 

 minute rounded particles, all forming an irregular spongy 

 mass of an iron gray color and metallic luster. Between this 

 are small crystals, not over 5 mm in diameter, apparently hexag- 

 onal and much resembling forms of polybasite, produced by 

 twinning. The material for the analysis (b) was selected with 

 great care, but, as the results show, gave the composition of 

 aguilarite, slightly contaminated with a sulphantimonide. 



a. b. 



Ag 79-41 80-27 ' 



S 5-93 6-75 



Se 13-96 12-73 



Cu 050 0-07 



Fe 0-26 



Sb ; 0-41 



99;80 100-49 



c. Similar crystals, as mentioned under b, were found on 

 quartz, associated with calcite, some of them were over 10 mm 

 in diameter. On examination with a lens they could easily be 

 seen to be made up of different minerals and were evidently 

 the result of the alteration of aguilarite into stephanite, as 

 previously described, with metallic silver, argentite, etc. The 

 outer portion was brittle, the inner malleable — but neither 

 could be obtained in a state of purity. They gave : 





Brittle 



portion. 







Malleable 



portion. 





Ag- 



67-58 



or 



Ag,S... 



62-85 



Ag... 



84-05 oi 



' Ag.... 



25-28 



Cu._ 



6-83 





Ag 2 Se _ . 



16-35 



Cu.._ 



1-83 



Ag 2 S.. 



55-49 



Fe__ 



0-42 





CuS .... 



9-27 



Fe... 







Ag 2 Se . 



14.28 



Sb .. 



6-83 





FeS_... 



0-56 



Sb... 



1-24 



CuS . . . 



2-75 



As.. 







Sb„S 3 



9-56 



As... 



0-28 



Sb 2 S 3 .. 



1-74 



Se .. 



3-51 













Se ... 



3-82 



As 2 S 3 .. 



0-46 



S ... 



14-76 













S .... 



8-76 









99-93 98-59 99-98 100*00 



These crystals had been considered to be a new species. 



d. In the lot of aguilarite specimens was noticed a small 

 piece of quartz and calcite with solid dodecahedral crystals, 

 mostly distorted, from l-2 mm in size. As there was no indica- 



