162 DESCRIPTIONS OF MINERALS. 
Tin is also used extensively as tinfoil ; but most tinfoil consists be- 
neath the surface of lead,and is made by rolling out plates of lead coated 
with tin. With quicksilver it is used to cover glass in the manufac- 
ture of mirrors. ‘Tin oxide (dioxide), obtained by chemical processes, 
is employed, on account of its hardness, in making a paste for sharp- 
ening fine cutting instruments, and also tosome extent in the prepara- 
tion of enamels. The chlorides of tin are important in the precipita- 
tion of many colors as lakes, and in fixing and changing colors in dye- 
ing and calico-printing. The bisulphide has a golden lustre, and was 
termed aqurum musivum, or mosaic gold, by the alchemists. Itismuch 
used for ornamental painting, for paper-hangings and other purposes, 
under the name of bronze powder. 
TITANIUM. 
Titanium occurs in nature combined with oxygen, form- 
ing titanium dioxide or titanic acid, and also in oxygen com- 
binations with iron and calcium, and in some silicates. It 
has not been met with native. 
The ores are infusible alone before the blowpipe, or nearly 
so. ‘Their speeute gravity is between 3:0 and 4:0. 
Rutile. 
Dimetric. In prisms of four, eight, or more sides, with 
pyramidal terminations, and often bent as in 
* v. bvhe figure; 1AL=123° 73. Crystals often 
s t acicular, and penetrating “quartz. Some- 
times massive. Cleavage lateral, somewhat 
distinct. 
Color reddish-brown to nearly red ; streak 
very pale brown. Lustre submetallic-ada- 
mantine. ‘Transparent to opaque. Brittle. 
He —— 6 06D. Ge = tt 
Composition. TiO, = Oxygen 39, titanium 61 = 100. 
Sometimes contains iron, and has nearly a black color ; this 
variety is called Nigrine. B.8B. alone unaltered ; with salt 
of phosphorus a colorless bead, which in the reducing flame 
becomes violet on cooling. 
Diff. The peculiar subdamantine lustre of rutile, and 
brownish-red color, much lighter red in splinters, are striking 
characters, It differs from tour maline, :docrase, and augite, 
by being unaltered when heated alone before the blowpipe ; 
and from tin ore, in not affording tin with soda ; from 
sphene in its crystals. 

[EBON 
Ce eee Ok 

