OBIi OF TIN. 2J3 



The analysis of warwickite, by Smith and Brush, has shown that it 

 contains 20 per cent, of boracic acid, and therefore is a borotitanate. 



Schorlomite. Black, and often irised tarnished. Streak grayish- 

 black. H — 7 — 7 f 5. Gr — 3 80. Fuses readily on charcoal. Easily 

 decomposed by the acids, and gelatinizes. Near gadolinite. From the 

 Ozark Mountains, Arkansas. 



Besides the ores here described, titanium is an essential 

 constituent also of ilmenite, (titanic iron) ; also in the zir- 

 conia and yttria ores ceschynite, airstedite, and polymignite, 

 and in some other rare species ; sometimes in pyrochlore. 



The metal titanium has seldom been obtained in the me- 

 tallic state, and is not used in the arts. The uses of the 

 oxyd have been mentioned. 



6. TIN. 



Tin has been reported as occurring native. There are 

 two ores, the oxyd and a sulphuret. It also occurs in some 

 ores of columbium. The specific gravity of the, sulphuret is 

 between 4*3 and 4*4 ; that of the oxyd, between 6*5 and 7*1. 

 With carbonate of soda on charcoal, a globule of tin is ob- 

 tained. When the tin is in minute quantities in a mineral, 

 it is well to add also some borax, and by this means, especi- 

 ally if any iron present be first removed, or if it be only in 

 small quantaties, even a $ per cent, of tin may be detected. 



\^\ JVative tin is found in gray metallic grains in the gold ?*i. 

 washings of the Ural. The crystals of pure tin are either 

 tesseral (cubic), or dimetric, this metal being dimorphous. 



tin pyrites. — Sulphuret of Tin. 



In cubes and massive. Color steel-gray or yellowish 

 Streak black. Brittle. H=4. Gr = 4\3— 4-6. 



Composition : sulphur 30, tin 27, copper 30, iron 13. 



Obs. This rare ore has been found only in Cornwall, 

 where it is often called bell-metal ore, from its frequent 

 bronze appearance. 



How does tin occur in the mineral kingdom ? How is it detected 

 y the blowpipe? What is the appearance and coir position of tin 

 yrites ] 



