18 Dr Rose on Zinkenite, a New Mineral Species. 



The faces marked M are usually deeply striated in a longi- 

 tudinal direction ; the inclined faces, though not streaked, are 

 uneven, and by no means smooth. The fracture is uneven, 

 and does not present any traces of cleavage. The lustre is 

 very bright metallic ; the colour of the crystals themselves, 

 and of their powder, is steel-grey. 



The hardness is between 3.0 and 3.5, a little more consi- 

 derable than that of calcareous spar. The specific gravity I 

 found = 5.303, at a temperature of 10° R. Another experi- 

 ment gave 5.310, at a temperature of 10 \°. 



The crystals are aggregated in groups presenting a colum- 

 nar composition ; they occur on massive varieties of the same 

 species, in massive quartz. Their length often exceeds half 

 an inch, their breadth two or three lines, but frequently they 

 are also very thin, and form together fibrous masses. 



When heated alone before the blowpipe on charcoal, the 

 Zinkenite briskly decrepitates, and melts as easily as the grey 

 antimony. Small metallic globules are formed, which are en- 

 tirely volatile, on the blast being continued, while the char- 

 coal is covered with a white coating of oxide of lead, and at a 

 little greater distance from the globules with a white perfectly 

 volatile coating of oxide of antimony. In the mattress it de- 

 crepitates and melts ; near the assay a small quantity of the 

 same kind of black sublimate is formed, as when we treat the 

 grey antimony in the same manner ; at a little greater dis- 

 tance, a yellow substance is deposited, which becomes white 

 on cooling, and may be entirely volatilized. When heated in 

 a glass tube, it decrepitates and melts ; a dense white smoke 

 fills the tube, and is condensed in the colder parts of the tube, 

 but this deposit cannot be entirely volatilized. Near the as- 

 say a melted yellow mass of oxide of lead is visible. The 

 air passing through the tube has a strong smell of sulphu- 

 rous acid. With soda, the mineral yields many globules of 

 metallic lead. 



Zinkenite is found in the antimony mine of Wolfsberg, 

 near Stolberg, in the south-eastern part of the Hartz. 



Several years ago, the specimens of the mineral described 

 above, were given to me by Mr Zinken, the director of the 

 Anhalt mines ; in compliment to him, I propose the name of 



