244 Ford — Stephanite Crystals from Arizpe, Mexico. 



Akt. XXVIII. — Stephanite Crystals from Arispe, Sonora 7 

 Mexico • by W. E. Fokd. 



Recently two remarkable specimens of stephanite were sent 

 by Mr. J. W. Miller to Prof. L. D. Huntoon of the Mining 

 Department of the Sheffield Scientific School and were kindly 

 given to the writer by the latter for investigation. They were 

 found at the J. Pedrazzini mine at Arizpe, Sonora, Mexico, in 

 a narrow but rich silver vein in which the stephanite occurs 



associated with polybasite, argentite, the ruby silvers and the 

 native metal. 



The stephanite crystals are of two types ; the first showing 

 crystals of simple form but of extraordinary size ; the second 

 type being of small but highly modified crystals which were 

 found on the back of the specimens and projecting into the 

 cavities. The two widely divergent types of crystals represent 

 undoubtedly two different periods of formation. The large 

 type of crystals is somewhat diagrammatically represented "in 

 figure 1, which was sketched from the smaller of the two speci- 

 mens and is reproduced nearly in its natural size. The crystals 

 have the form of short thick hexagonal prisms, being pre- 



