214 



METALS. 



tin ore. — Oxyd of Tin. 



Dimetric. In modified square prisms and octahedrons 

 ./'Vv. often compound : e : e=121° 

 y\ • \A 40' ; a : a (over the summit) 



V-/ ^h 112° 10' ; a : a (over a ter- 

 minal edge) 133° 31'; M : 

 e=133° 34'; M : e=135°. 

 Cleavage indistinct. Also 

 \^~\>^/ massive or in grains. 



^^^/^ Color brown or black, with 



a high adamantine luster when in crystals. Streak pale 

 gray to brownish. Nearly transparent to opaque. H=6 — 

 7. Gr=6-5— 7-1. 



Composition : when pure, tin 78*38, oxygen 21*62 ; often 

 contains a little oxyd of iron, and sometimes oxyd of colum- 

 bium. Before the blowpipe alone, infusible ; with soda, 

 affords a globule of tin. 



Stream tin is the gravel-like ore found in debris in low 

 grounds. Wood tin occurs in botryoidal and reniform shapes 

 with a concentric and radiated structure ; and toad's-eye tin 

 is the same on a small scale. 



Dif. Tin ore has some resemblance to a dark garnet, 

 to black zinc blende, and to some varieties of tourmaline. It 

 is distinguished by its infusibility, and its yielding tin before 

 the blowpipe on charcoal with soda. It differs from blende 

 also in its superior hardness, and in giving no fumes on char- 

 • coal before the blowpipe. 



Obs. Tin ore occurs in veins in the crystalline rocks 

 granite, gneiss, and mica slate, associated often with wolfram, 

 copper and iron pyrites, topaz, tourmaline, mica or talc, and ■ 

 albite. Cornwall is one of its most productive localities. 

 It is also worked in Saxony, at Altenberg, Geyer, Ehren- 

 friedersdorf and Zinnwald ; in Austria, at Schlackenwald and 

 other places ; in Malacca, Pegu, China, and especially the 

 Island of Banca in the Ea«t Indies. It has also been found 

 in Galicia, Spain ; at Dalecarlia in Sweden ; in Russia ; in 

 Mexico, Brazil, and Chili ; in the United States, at Chester- 

 field and Goshen, Mass., in some of the Virginia gold mines, 



What is the crystallization of tin ore ? Mention its other physical 

 characters 1 What is its composition and blowpipe reactions 1 What 

 is stream tin ? wood tin, and toad's eye ? How is tin ore distinguished 

 from garnet, blende, and tourmaline ? 



