Intelligence and Miscellaneous Articles. 149 



nied by quartz, which appears to be a more ancient formation, and 

 tinstone, which is more recent. It was long taken for brown spar 

 (dolomite), for it is red or reddish- white in crystals, and presents in 

 its combinations P, x, T, and /, so that the last three forms, with 

 nearly equally extended surfaces, resemble a rhombohedron. 



Freshly broken, the crystals are semi-transparent, cleavage rec- 

 tangular, in the direction of the faces P and M ; hardness 7f (of 

 Breithaupt's scale); specific gravity 2'441 to 2445. 



Decomposed by hydrofluosilicic acid, M. Kroner obtained as its 

 chemical composition, — 



Silica 66-43 i 



Alumina 17*03 



Oxide of iron 0*49 



Potash 1396 



Soda 0*91 



Lime 103 



Magnesia and manganese. . traces 



Poggendorff's Annalen. 



CHEMICAL ANALYSIS OF COPPER BLENDE. BY C. F. PLATTNER. 



Breithaupt's copper blende has recently been said to be identical 

 with tennantite. The former however is distinguished by its red 

 streak and lower specific gravity. In tennantite from Cornwall, 

 Kudernatsch found — 



Sulphur 27*76 



Arsenic 19- 10 



Copper 48-94 



Iron 3*57 



Silver trace 



Quartz 0-08 



99-45 

 The chemical formula for which is — 



(Cu % } As * S > + 2 < Cu * S > 4 ' As * S " 

 or more simply, according to M. Frankenheim, 



(Ci 



(Fe 



Copper blende from the Prophet Jonas Mine, Freiberg, I found to 

 contain — 



Sulphur...,. 28-111. .201-16 = 0139 =139 



Arsenic 18-875 47004 = 0040. = 40 



Copper 41070 395-69 = 0104 =104 



Zinc 8-894 403-23 = 0022 1 _ 90 



Iron 2219 33921 = 0'007 J — 



Lead 0341 



Antimony and silver. . traces 



99510 





