404: Koenig — Wew Species Melanochalcite and Keweenawite. 



Keweenawite. With Notes on some other Ttnown species ; 



Art. XXXYIII. — On the New Species Melanochalcite and 

 Keweenawite. With No^ 

 by George A. Koenig. 



1 . Melan ochalcite. 



For the material of this investigation 1 am indebted to 

 Captain James Hoatson, of Cahimet. I received it early in 

 January of 1902, and informed that gentleman — about January 

 17th — that I had much reason to distinguish the black mineral 

 as a new mineral species, for which I proposed the name 

 melanochalcite (from /LteXa? and ^aX/co?). 



Occurrence. — The material comes from the exploration shaft 

 of the Calumet and Arizona Copper Mining Company, near 

 Bisbee, Arizona. I am informed by Captain Hoatson that 

 these specimens represent the character of the ore at a depth 

 of 800 feet. All the mines in that district exhibit oxidized 

 ores to a very considerable depth. Sulphides are rare. I had 

 examined and assayed a number of samples for Captain Hoat- 

 son from time to time as the sinking of the shaft proceeded ; 

 all oxide ores, and of exceptional richness. Ko samples assayed 

 under 10 per cent copper. Cuprite was always preponderating, 

 sometimes mixed with much hematite ; say, for instance, 30 per 

 cent of the former to TO per cent of the latter, as an extreme. 

 Malachite and chrysocolla appeared sparingly ; noazurite ; whilst 

 at the Copper Queen Mine, of the same belt, the silicate and the 

 carbonates are in the foreground. The material under consid- 

 eration in this paper differs from that of the upper shaft. 

 The material before me presents hard spheroidal nodules, 

 cemented together by a soft, brown-red, clayey material, easily 

 removable. The nodules' nucleus is formed by granular 

 cuprite, with occasional druses, the latter lined with octa- 

 hedral crystals. This kernel is surrounded by a zone of 

 pitchy-black mineral, a few millimeters in thickness. Upon 

 this follows a banded green zone of chrysocolla and malachite. 

 Thereupon follows white, or transparent, quartz. Within the 

 quartz are smaller cuprite kernels, each with its aureole of 

 black and green. Here the black material is thicker, but less 

 pure as a whole. The purest substance is always thin, lying 

 close to the cuprite. It passes into deep olive green : then 

 light olive-green into the pure green of chrysocolla, or mala- 

 chite. Thus the fracture-surface of a nodule is of striking 

 beauty. The one before me, which served as model for the 

 description, has an average diameter of 120 millimeters. The 

 kernel is not centric, and rather oblong than circular. The 

 black, green and white parts are massed chiefly on one side. 



