ZINC ORES. 271 



alone, but yields a yellow transparent glass with borax. Dis. 

 solves in nitric acid, without effervescence. 



Dif. Resembles red stilbite, but distinguished by its in 

 fusibility and also by its mineral associations. 



Obs. Occurs with Franklinite at Franklin and Sterling, 

 N. J. 



Uses. A good ore of zinc when abundant, and easily re- 

 uced. It may be readily and economically converted into 

 ulphate of zinc, or white vitriol. 



Voltzite. A compound of sulphuret and oxyd of zinc. Occurs in 

 mplanted globules of a dirty rose-red color, with a pearly luster on a 

 leavage surface. From France. 



goslarite. — sulphatb of zinc. — White Vitriol. 



Trimetric. Cleavage perfect in one direction. Crystals 

 rhombic prisms, of 90° 42'. 



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

 tringent metallic, and nauseous. Brittle. H=2 — 2*5. — 

 Gr=l-9— 2-1. 



Composition : oxyd of zinc 28*09, sulphuric acid 27*97, 

 water 43*94. Gives off fumes of zinc when heated on char- 

 coal, which cover the coal. 



Obs. Results from the decomposition of blende. Occurs 

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

 Wales. 



Uses. Sulphate of zinc is extensively employed in medi- 

 cine and dyeing. For these purposes it is prepared to a large 

 extent from blende, by decomposition like pyrites, though 

 this affords, owing to its impurities, an impure sulphate. It 

 is also obtained by direct combination of zinc with sulphuric 

 acid ; zinc is exposed to the action of dilute sulphuric acid, and 

 the solution obtained is then evaporated for crystallization. 

 The red oxyd of zinc, of New Jersey, may become an abun- 

 dant source of this salt. 



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

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

 and agitating till it cools and presents an appearance like 

 /oaf sugar. 



How does it differ from red stilbite 1 For what may it be W¥>d 1 

 What is the appearance and taste of white vitriol 1 Of what does il 

 onsist 1 How is it formed ? For what is it used 1 



