154 



DESCRIPTIONS OF MINERALS. 



Nevada produced 10,000 tons in 1870, and 50,000 in 1875. According 

 to Phillips, England produced in 1^72, (50,450 tons ; Prussia, in 1871, 

 49,500 tons ; Spain, in 1873. 102,600 tons ; France, 2,500 tons ; Italy, 

 15,500 tons ; Austria, 10,000 tons. 



ZINC. 



Zinc occurs in combination with sulphur and oxygen ; 

 and also in the condition of silicate, carbonate, sulphate, 

 and arsenate. It is also a constituent of one variety of the 

 species spinel. The chief sources of the metal are smith- 

 sonite or the carbonate ; willemite and calamine, or sili- 

 cates ; zincite, or the oxide ; sphalerite (blende), or the 

 sulphide ; and franklinite. 



Sphalerite. — Blende. Zinc Sulphide. 



Isometric. In dodecahedrons, octahedrons, and other allied 

 forms, with a perfect dodecahedral cleavage. Also massive ; 



sometimes fibrous. Color wax-yellow, brownish-yellow, to 

 black, sometimes green, red and white ; streak white, to red- 

 dish brown. Lustre resinous or waxy, and brilliant on a 

 cleavage face ; sometimes submetallic. Transparent to sub- 

 translucent. Brittle. H. =3-5-4. G-. =3 -9-4-2. Some 

 specimens become electric with friction, and give off a yel- 

 low light when rubbed with a feather. 



Composition. ZnS = Sulphur 33, zinc 67 = 100. Contains 

 frequently a portion of iron sulphide when dark colored ; 

 often also 1 or 2 per cent, of cadmium sulphide, especially 

 the red variety. Nearly infusible alone and with borax. 

 Dissolves in nitric acid, emitting sulphuretted hydrogen. 

 Strongly heated on charcoal yields fumes of zinc. 



Biff. This ore is characterized by its waxy lustre, perfect 

 cleavage^ and its being nearly infusible. Some dark varieties 

 look a little like tin ore, but their cleavage and inferior 

 hardness distinguish them ; and some clear red crystals, 



