270 tin. 



crystals is a rectangular four-sided prism, terminated by four-sided 

 pyramids, fig. b ; another form, the dodecahedron, with triangular 

 planes, is represented fig. c. The primitive form is an obtuse 

 octahedron, fig a. The structure of the crystals is lamellar ; 

 externally they are splendent, the cross fracture is uneven, and the 

 lustre shining or resinous. Tinstone varies from semitransparent 

 to opaque : it gives sparks with steel ; it is very heavy, brittle, and 

 yields a greyish-white streak. Its specific gravity is 6'970. 

 Before the blow-pipe pulverised tinstone decrepitates, and is 

 reduced to the metallic state. Its constituents are, tin 77*5, 

 iron 0*25, oxygen 21*5, silica 0'75. Klaproth. — This ore occurs 

 disseminated, in veins or beds, in granite, gneiss, mica-slate, and 

 clay-slate. Cornwall is the most considerable repository of this 

 mineral in Europe. It is also found in considerable abundance in 

 the Saxon Erzgebirge ; in Monte Rey, in Gallicia, in Spain, and 

 in various parts of Asia j and South America. The grains and 

 fragments of tinstone found in alluvial soil are separated from the 

 earthy matter by passing streams of water over them, whence these 

 grains are called stream-tin. Tinstone is readily distinguished 

 from wolfram by its extreme hardness ; from blende by its superior 

 hardness, and by its not emitting a sulphurous odour when tritu- 

 rated ; from garnet by its peculiar lustre and density ; and from 

 shorlby its colour, form, and greater specific gravity* 



Wood Tin.— Kornisch Zidnerz, Werner; Etain oxide con- 

 cretionne, Hauy. — It is found with stream-tin in reniform, 

 globular, botryoidal, and wedge-shaped pieces. Its most common 

 colour is hair-brown. The structure is divergingly fibrous, with 

 concentric lamellae ; the lustre is glistening and silky : it is opaque, 

 softer than common tinstone, and brittle. Its specific gravity is 

 6*4. It consists, according to Vauquelin, of tin 91, oxide of 

 iron 9. It is readily distinguished from brown hematite by its 

 greater hardness and superior specific gravity. 



Tin Pyrites. — Zinnkies, Werner; Etain sulphure, Hauy. — 

 The colour of this ore varies from steel-grey to brass-yellow ; the 

 lustre is glistening and metallic. It occurs massive and dissemi- 

 nated. Its fracture is even, and sometimes conchoidal. It yields 

 easily to the knife, and is brittle. Its specific gravity is 4*3. Its 



