406 Koenig — New S^peoies Melanochalcite and Keweenawite. 



^^|^ = 4-141 at 21 C. (material " C ")• This number is 



rather under than above the true weight, because I wished to 

 avoid boiling, in order not to interfere with the water-per- 

 centage of the material. To even up matters, the water used 

 was saturated with air at 21 C. for both weighings. 



Chemical Examination. — B. B. In closed tube the sub- 

 stance looses water and CO, and the coffee-brown powder turns 

 to brown black. With tlie fluxes only copper reaction, except 

 with microcosmic salt, when a fine skeleton of SiO, appears in 

 a blue glass. The mineral is readily decomposed by HCl of 

 all concentrations, even when in coarse fragments. If such a 

 fragment be placed in 3 per cent HCl, and one observes with a 

 pocket lens, one sees the margins of the splinter turn white. The 

 white zone widens steadily, until nothing but a white mass 

 remains, which occupies the entire space of the original black 

 substance. And yet the percentage of SiO, is not quite 10. 

 While this dissolution is progressing one sees a steady spray 

 arise of minute bubbles of CO,, very different from the big air 

 bubbles arising from the microscopic capillary fissures. I con- 

 sider this behavior as the essential foundation of my hypothesis 

 regarding the constitution of the molecules of this mineral — 

 to wit: SIO^ and CO^ are simultaneously liberated^ whilst 

 CuO and H^O pass into the solution. The resultant Si02 is 

 what I would call semigelatinous — not colorless and transpar- 

 ent, but w^iite and translucent. It is readily dissolved by the 

 water solution of NaHO. There is no cuprous chloride formed. 

 The copper is altogether cupric. 



Material "A." — preliminary analysis. Weight of substance 

 taken, 0-5361 gr. 



0-0671 loss by ignition. 

 0-0532 SiO, 

 0-0010 Fe.Og 

 0-4188 Cu,S 



The sulphide was dissolved and electrolyzed, yielding 0-3277 

 Cu=0-4107 CuO, to which must be added 0*00015 CuO, 

 obtained from the electrolyte by H,S. Total, 0-4122 CuO. 



Ln percentage : 



CuO 



ZZl 



76-72 



SiO, 



z= 



9-91 



H.0| 



CO, j 



= 



12-52 



Fe,03 



'— 



0-19 



99-34 



