Koenig — Neio Species Melanochalcite and Keweenaiuite. 415 



f. Pulveriform chalcocite from the Champion Mine. 



This very interestiDg material was also encountered in a 

 small cross vein and recognized by Dr. L. L. Hubbard as some- 

 thing peculiar. ]N"either of us thought of chalcocite. It soils 

 the paper or fingers like soft pyrolusite or graphite. An 

 aggregate of small crystals, the largest less than O-S^^"^ to micro- 

 scopic individuals. 



The dust appears under the microscope as made up of single 

 hexagonal plates, or groups of plates, easily disengaged and 

 reduced to individuals, perfectly opaque. I have since observed 

 this same substance both at the Champion and Mass mine, 

 dusting over groups of calcite crystals, either loosely or firmly 

 imbedded in the calcite, causing the latter to -'look gray or 

 black. It becomes bluish by tarnish. B. B. reacts for copper 

 and sulphur only. The record of the quantitative analysis is 

 lost ; but I remember distinctly that the percentage of copper 

 was close to 79. 



g. ISTodular nuggets found in the coarse material from the 

 mortar at the stamp mill of the Baltic mine were singled out 

 by Mr. William Yivian as whitneyite. If seen by themselves 

 they look much like rounded native copper ; but seen along- 

 side of the latter a difference becomes noticeable even to 

 the untrained eye. Compared with one another, on filed or 

 ground surface, slighter differences appear. Held in a vise, a 

 strong blow with a cold-chisel will break the whole in two. 

 ISTative copper will not do this. The fracture is hackly ; there 

 are small geodes of calcite. Calcite is visible between the 

 imperfect crystals of gray color. But the lens also reveals 

 minute black globular bodies. These latter I succeeded in 

 identifying as chalcocite. The material for analysis was 

 extracted with diluted HCl. After extraction material 

 weighed 0'4003 gram. 



0-4575; Mg2As20.= 



It 



gave 



: InsolubL 

 0-0555 



es — 0-0081 ; 



Cu,S 



H< 



snce : 



Cu = 



As = 

 Quartz = 



91-33 : 

 6-60 : 

 2-20 



; 63 = 

 : 75 = 



1-450 



0-0888 



100-13 Cu : As = 16-22 : 1 



A, From Captain James Hoatson, of Calumet, I received a 

 specimen showing quartz and what looks like native copper, at 

 first sight. The supposed native copper is similar in color to 

 the nodules just described; also similar in hardness and rela- 

 tive toughness. A filed surface shows a very uniform, dense 

 texture, with a decided yellowish, brassy, color ; but etched 



Am. Jour. Sci.— Fourth Series, Vol. XIY, No. 84. — December. 1902. 

 29 



