USEFUL METALS 257 



commercial zinc is readily soluble in the mineral aeMs. It burns 

 in an atmosphere of oxygen with a bluish flame to zin<- <>\i<l<-. 

 Its specific gravity is 7.1; melting point 419 C., boiling point, 

 918, and its atomic weight is 65.37. 



Ores of the Metal. Native Zinc, Zn, 100 per cent. Zn. Thi> 

 metal has boon reported from ea-teni Alabama and from m-ar 

 Melbourne, Australia, but the occurrences are not coraplett ly 

 authenticated. 



Sphalerite, ZnS, 67 per cent. Zn. Often with resinous luster. 

 (Isometric). 



Wurtzite, ZnS, 67 per cent. Zn. Many massive blendes are 

 mixtures of these two minerals. (Hexagonal.) 



Smithsonite, ZnCOs, 51.96 per cent. Zn. When earthy and 

 impure it is called dry bone by American miners. 



Hydrozincite, 2ZnCO 3 ,Zn(OH) 2 , 60 per cent. Zn. 



Zincite, ZnO, 80.3 per cent. Zn. Deep red to orange yellow. 



Franklinite, (Fe,Mn,Zn)0,(Fe,Mn)2O 8 . A spinel of variable 

 composition. 



Voltzite, 4 ZnS, ZnO. A rather rare oxy sulphide of zinc. 



Goslarite, ZnSO 4 ,7H 2 O, 28.2 per cent. ZnO. 



Calamine, ZnSiO 3 ,Zn(OH) 2 , 54.2 per cent. Zn. 



Willemite, Zn 2 Si04, 58.5 per cent. Zn. 



Origin of the Ores. Zinc is fairly common but not widely 

 diffused in nature. Dieulafait reports its occurrence in sea water. 

 It has also been found in the ashes of sea weeds. The occurrence 

 of native zinc in northeastern Alabama, in Shasta County, 

 California, and near Melbourne, Australia, need confirmation. 

 If native zinc occurs in these localities it is probably a reduction 

 product. 



The sulphide of zinc is by far the most important source of the 

 metal. It is known as sphalerite, blende, or black-jack when 

 crystallized in the isometric system, and as wurtzite when in 

 the hexagonal system. The massive blendes are mechanical 

 mixtures of these two minerals. The sulphide of zinc is precipi- 

 tated in the laboratory by the action of ammonium sulphide 

 upon the soluble salts of zinc, or by the action of hydrogen sul- 

 phide upon an alkaline solution of the metal. According to 

 H. de Senermont, sphalerite is formed when zinc solutions are 

 heated in a sealed tube in an atmosphere of hydrogen sulphide. 

 According to F. W. Clarke, sphalerite is formed in nature at 

 relatively low temperatures and at the higher temperatures it is 



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