91 
for their varieties of color and richness of luster, making them 
very attractive to the eye. They are made up chiefly of the car- 
bonate, smithsonite. 
Specimens illustrating the process of extraction of zinc, are 
shown in Case lo. 
TIN. 
Case 11 .— Tin ore from South Dakota. The tin is in the 
form of cassiterite^ a black oxide which can be seen scattered 
through the granite. This is the universal ore of tin, containing 
about 78 per cent, of the metal. Some specimens of stream tin are 
also shown. This is formed by disintegration of the rocks con- 
taining the ore, and removal of the lighter minerals by running 
water. The cassiterite being very heavy stays behind and is found 
in the bed of the stream. 
Case 12.— Tin ore, New South Wales. See also the pyra- 
mid of this ore in the West Dome. 
Case 13. — Tin ore from the famous Cornwall Mines of 
Great Britain, which have been in operation many centuries. 
Process of reduction of tin ores illustrated by specimens from 
the Redruth Smelting Co. 
MERCURY. 
Case 15. — A series of ores mercury and cimtabar 
and the rocks associated with them, from the New Almaden 
mines, California. Cinnabar is the red sulphide and the mineral 
from which mercury is chiefly obtained. Stages in the process of 
roasting the ore for extraction of the metal are shown, and a chart 
near by illustrates the kind of furnaces used. Mercury ores fron^ 
Spain and New Granada, S. A., are also shown. 
