Properties of some Minerals and their varieties. 265 
The + varieties are distinguished here, as in all other cases 
mentioned, by their specific gravity.* For the sake of com- 
arison, kobellite has been added; in it, the negative charac- 
ter of the lead and bismuth is neutralized by antimony. What 
part the admixture of Sb, As and Ag play in galenite is uncer- 
tain. We note here that we found bismuthinite to be — but 
boulangerite 0. 
F. Cobaltite. 
to the excess of the elements Co and As: only a quarter of 
them were positive. The crystals themselves are homogeneous 
and, unlike those of glaucodot, show no difference between 
h 
according to crystalline form. 
No. crystals investigated. 
49 
ube prominent + 
Octahedrons ‘“ 242 — 
Pyritohedrons “ 32 i a 
5 “ “ aes 
_ 
20 
Cube, octahedron and 115 
pyritohedron combined } 24 
Rose regarded the + character in this species as dependent 
upon the right or left hemihedrism. A proof to the contrary, 
from the consideration of the crystalline form, 1s not possible, 
as the proof itself lies in the supposition, It is of more im- 
* In consideration of the high values of the specific gravity, it is perhaps desir- 
able for us to mention our method of determination. We had at our disposal 
two balances: a balance made by Kusche in Vienna (maximum _— — grams), in 
the Mineral Cabinet; and another ry maximum 50 grams), 
private property of Schrauf, We avoided the use of  pygnometer, and adopted 
in preference the method i in air and water. mae 
