156 DESCRIPTIONS OF MINERALS. 



Goslarite.— Sulphate of Zinc. White Vitriol. 



Trimetric. Cleavage perfect in one direction. 2" A i== 

 90° 42'. 



Color white. Lustre vitreous. Easily soluble ; taste as- 

 tringent, metallic, and nauseous. Brittle. H. =2-2 '5. G. = 

 1-9-2-1. 



Composition. Zn0 4 S + 7 aq. =Zinc oxide 28*2, sulphur 

 trioxide 27*9, water 43-9 = 100. B.B. gives off fumes of 

 zinc on charcoal, which cover the coal. 



Ols. Eesults from the decomposition of blende. Occurs 

 in the Hartz, in Hungary, in Sweden, and at Holywell in 

 Wales. 



Sulphate of zinc is extensively employed in medicine and 

 dyeing. For these purposes it is prepared to a large extent 

 from blende by decomposition, though this affords, owing to 

 its impurities, an impure sulphate. It is also obtained by 

 direct combination of zinc with sulphuric acid. 



White Vitriol, as the term is used in the arts, is one form 

 of sulphate of zinc, made by melting the crystallized sul- 

 phate, and agitating till it cools and presents an appearance 

 like loaf sugar. 



Kottigite. A hydrous zinc-cobalt arsenate of reddish color (owing 

 to presence of cobalt) from Schneeberg 



Adamite. A hydrous zinc-arsenate of honey-yellow to violet color, 

 from Chili. 



Smithsonite. — Carbonate of Zinc. 



Ehombohedral. R A 72=107° 40'. Cleavage R perfect. 

 Massive or incrusting ; reniform and stalactitic. 



Color impure white, sometimes green or brown ; streak 

 uncolored. Lustre vitreous or pearly. Subtransparent to 

 translucent. Brittle. H. =5. G. =4*3-4*45. 



Composition. Zn0 3 C = Carbon dioxide 35*2, zinc oxide 

 64*8 (four-fifths of which is pure zinc) = 100. Often con- 

 tains some cadmium. B.B. infusible alone, but carbonic 

 acid and oxide of zinc are finally vaporized. Effervesces in 

 nitric acid. Negatively electric by friction. 



Diff. The effervescence with acids distinguishes this 

 mineral from the following species; and the hardness, diffi- 

 cult fusibility, and the zinc fumes before the blowpipe, from 

 the carbonate of lead or other carbonates. Besides, the 

 crystals over a drusy surface terminate usually in sharp 

 three-sided pyramids. 



