160 DESCRIPTIONS OF MINERALS. 
Cassiterite.—Tin Ore. Tin Oxide. 
Dimetric. In square prisms and octahedrons; often com- 
te poundeds: 17. 18 ke 40a 2. 
Ait (Over, the siimmit)) 22 
10’, (over a terminal edge) 
133° 31’. Cleavage indistinct. 
Also massive, and in grains. 
Color brown or black, with 
a high adamantine lustre when 
in crystals. Streak pale gray 
f~ to brownish. Nearly trans- 
parent to opaque. H.=6-7. G.=6-4-7-L. 
Composition. Sa O,=Oxygen 21°33, tin 78°67 ; often con- 
tains a little iron, and sometimes tantalum. 
B.B. alone infusible. On charcoal 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. 
Diff. 'Tin ore has some resemblance to a dark garnet, to 
black zine blende, and to some varieties of tourmaline. It is 
distinguished by its infusibility, and its yielding tin before 
the blowpip2 on charcoal with soda. It differs from blende 
also in its superior hardness. . : 
Obs. Tin ore occurs in veins in the crystalline rocks, 
granite, gneiss, and micaslate, associated often with wolfram, 
copper and iron pyrites, topaz, tourmaline, mica or tale, 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 East Indies; in Queensland and 
Northern New South Wales, Australia, in large quantities ; 
in Greenland. It occurs also in Galicia, Spain; at Dale- 
cara in Sweden; in Russia; in Mexico at Durango; 
and Bolivia. In the United States it has been found spar- 
ingly at Chesterfield and Goshen, Mass.; in some of the Vir- 
ginia gold mines ; in Lyme and Jackson, N. H.; and in the 
Temescal Range, California. 
General Remarks.—The principal tin mines now worked, are those 
of Cornwall, Banca, Malacca, and Australia. 
The Cornwall mines were worked long before the Christian era. 

