8o THE PROSPECTOR'S HANDBOOK. 



TIN. 



When a tin-bearing mineral is heated before the blowpipe 

 with carbonate of soda or charcoal, white metallic tin is 

 yielded. By dissolving this in hydrochloric acid and adding 

 metallic zinc, the tin will be deposited in a spongy form. In 

 the blowpipe assay, tin leaves a white deposit behind it, which 

 cannot be driven off in either flame. If it be moistened 

 with nitrate of cobalt solution, the deposit becomes bluish 

 green, and this test distinguishes it from other metals. 

 The most important ore is 



Cassiterite (tin ore, oxide of tin, tinstone). 



Massive and in grains. 



Crystallization in square prisms, octahedral, &c. 

 Colour when pure, which is rarely the case, colourless 

 and transparent, but usually brown, sometimes 

 greyish or whitish, and occasionally reddish (as in 

 Australia) ; transparent red crystals are rare. 

 Nearly opaque, and a resinous, submetallic lustre. 

 Streak brownish. 

 H. 6 to 7; S.G. 6-5 to 7'1. 



(N.B. Is much harder than zinc blende, for which it 

 may, perchance, be mistaken. Is usually almost as 

 hard as quartz, scratching glass, &c.) 

 Contains, when pure, 78 per cent, of tin. 

 Is infusible alone before the B.F., but with carbonate of 

 soda metallic tin is yielded. Insoluble in acids, whereas 

 zinc blende is easily soluble in hydrochloric acid.* 



Stream Tin 



Is the ore found as rolled fragments of tinstone in the 

 beds of streams or low-lying gravels. 



Wood Tin 



Is an uncrystallized fibrous form of the mineral rather 

 like dry wood, generally of a light brown colour, variegated 

 with yellowish and dark concentric bands. 



Tin ore sometimes resembles dark garnets, black zinc 

 blende, &c. 



* As the S.G. is comparatively high, tinstone can be separated from 

 minerals, such as iron and copper compounds, in a lode or deposit by 

 " panning out." (Mispickel, however, has S.G. 6'3.) 



