222 PROCEEDINGS OF THE AMERICAN ACADEMY 



IX. 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



CRYSTALLOGRAPHIC NOTES. 

 By Oliver W. IIuntixgton. 



Communicated by the Corresponding Secretary, June 10, 1885. 



Crystals of Azurite from Arizona. 



The mineral cabinet of Harvard College has recently received, througli 

 the kindness of Mr. Godfrey Hyams, some very interesting groups of 

 azurite crystals. The specimens came from the mines of the Detroit 

 Copi>er Company, situated near Clifton in the extreme eastern por- 

 tion of Arizona, and I am indebted to Mr Hyams for the following 

 description of their occurrence. 



" The formation in which the deposits are situated is peculiar to 

 these mines, so far as I know. The zones or belts of copper occur 

 in a sort of felsite on a contact between lime and iron, the lime being 

 calcite and the iron an oxidized compomid of varying composition. 

 Specimens analyzed have given results which show that hematite, 

 liraonite, turgite, and clay iron-stone all occur. 



" The ore appears in different forms : — 



"1. Malachite, as fibrous, botryoidal, stalactitic, encrusting, and 

 massive. 



" 2. Azurite, fibrous, botryoidal, encrusting, massive, and lastly 

 crystallized. 



" The crystals occur in various ways; singly on or in different man- 

 ganiferous clays, in clusters like stilbite, in plates like nail-head spar, 

 and in columns around a central axis like rock-candy. 



" The two carbonates are in every phase of transition. "We have 

 malachite changing into azurite, that is, the malachite outside and 

 azurite inside, then the reverse, malachite pseudomorph after azurite, 

 and vice versa. Then again specimens of native copper occur in 

 parts covered with crystals of cuprite, and these crystals in turn in- 

 crusted with malachite. With these are also large masses of cuprite, 



