USEFUL A//.V.1/.S 177 



Ores of the Metal, \ntiir tin, Sn, 100 per cent. Sn. Often 

 with gold copper, platinum and iridu-mine. 



Ma nnite, Cu 2 S,FeS,SnS 2 , 27 per cent. Sn. Sometimes known 

 as "bell metal," on account of its bronze color. 



Cassiterite, SnO 2 , 78.67 per cent. Sn. The most important 

 ore. 



There are also a few run- tin minerals. Of these nonlenskiol- 

 dine, a borate of calcium ;ui<l tin, CaO, SnOj, B|O, is the \\\-\ 

 interest ing from a mineralogical point of view for it connect- tin 

 with the important mineralizer boron. 



Several varieties of cassiterite are known. If it occurs in 

 crystals or in masses it is known as tin stone. If in forms radia- 

 ting and fibrous closely resembling wood, it is called wood 

 tin. If in warty aggregations it is called toad's eye tin. If in 

 rounded grains of sand along the beds of streams it is known as 

 stream or placer tin. 



Origin of the Ores. Native tin which is very rare occurs only 

 in small quantities perhaps as a decomposition and reduction 

 product of other tin minerals. It occurs in grains in New South 

 Wales but its occurrence with gold in Siberia, in Bolivia, and at 

 Guanajuato, Mexico, are all doubtful. The native tin reported 

 from Bolivia is believed to be artificial. 



The association of stannite in Cornwall, England, with pyrite 

 and sphalerite, together with the occurrence of stannite at Zin- 

 wald in the Erzgebirge with sphalerite and galenite would imply 

 the deposition of the minerals from solution. This sulphide so 

 pronouncedly suggesting in its appearance varieties of "bronze" 

 or "bell metal" is called by the miners bell-metal ore.' 



Cassiterite is by far the most important source of the tin of 

 commerce. It is both primary and secondary in its origin. 

 According to F. W. Clarke, it has been repeatedly observed as a 

 furnace product formed by the direct oxidation of tin. Accord- 

 ing to C. Doelter, cassiterite is perceptibly soluble in water at a 

 temperature of 80, but more soluble in the presence of 

 sodium fluoride. He also observed some crystallization from 

 such solutions. S. Meunier found 0.5 per cent, of cassiterite in an 

 opaline deposit somewhat resembling geyserite, from a thermal 

 spring in Selangor. J. H. Collins reports cassiterite as a cement 

 in certain Cornish conglomerates, also as impregnation deposits 

 in long buried horns of deer, as pseudomorphs after feldspar, 

 as cappings on crystals of quartz, as fissure linings in quartz, as 



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