142 Penficld and Kreider — Miiu < rahxjical Notes. 



specific gravity as the crystals. It was noticed, however, in 

 washing the pulverized mineral, that the crystals had a decided 

 tendency to float, owing - probably to the smooth surfaces that 

 they possess, combined with the fact that water does not seem 

 to wet them. By covering the powdered mineral with a shal- 

 low layer of water in a large beaker, and inclining the latter 

 so that a wave or ripple passes over the powder, the crystals 

 are readily brought to the surface, and by a little manipulation 

 almost a continuous layer of them can be made to float on the 

 water. By repeating this operation a number of times, and 

 making fractional separations, a product was finally obtained 

 which, when examined with a lens, showed only brilliant crys- 

 talline particles, and which could readily be made to float 

 wholly upon a limited surface of water. The mineral was 

 then further separated by means of the thallium-silver nitrate 

 fusion and, excluding the heavier and lighter, portions, a 

 product of intermediate specific gravity was reserved for the 

 chemical analysis. The specific gravity of this material, taken 

 with the pycnometer, was found to be 4*012. Iicepper gives 

 4-06-4-09 and Moore 3*907 for chalcophanite. 



The mineral when finely pulverized yielded a powder of a 

 dark chocolate-brown color. A qualitative analysis showed the 

 presence of iron, zinc, manganese and water. In the closed 

 tube water is given off at a very low temperature, and on 

 stronger ignition oxygen gas is liberated. The mineral is 

 readily soluble in hydrochloric acid with evolution of chlorine. 

 The results of the analysis are as follows : 



Ratio. 



139 ) 



225 \ 



FeO 1000 



ZnO 18-25 



MnO 48-27 -680 



O --. J 1-21 -701 



H 2 11-85 -658 



Insoluble -25 



361 





.Theory where 

 Fe:Zn = 8: 13 



1-07 



9-53 

 17-52 



2-00 



49-33 



2-06 



11-11 



1-94 



12-51 



99-83 



100-00 



The ratio of (Fe+Zn)0 : MnO : O : H 2 equals nearly 1:2: 

 2:2, indicating that the composition of the mineral can be 

 expressed by the formula KO, 2Mn0 2 , 2H 2 0, or KMn 2 6 , 2H 2 0, 

 where R = Fe and Zn in the proportion of about 8 : 13. The 

 above formula is identical with that derived by Moore* for 

 chalcophanite, except that in the material analyzed by him 

 iron was practically wanting and R=Zn and Mn. The agree- 

 ment between our analysis and the theory is quite satisfactory. 

 The water is a little low, but the material may have suffered a 

 slight alteration as it loses its water very readily, some going 



*Amer. Chemist, vi, p. 1, 1875. 



