69 
Pyrrhotite, with microscopic inclusions of pentlandite, sul- 
phide of iron, with sulphide of nickel. Nickel up to 3 per cent. 
Other minerals carry cobalt and nickel in small quantities, 
but are not important as sources of nickel. 
A collection of nickel and cobalt ores from all the important 
deposits of these metals. The most important ores of nickel 
are two: 1st, the sulphide of iron, pyrrhotite, which, in some 
localities carries minute inclusions of the sulphide of nickel, 
pentlandite, and second, the apple green silicate, garnierite. 
Nickel and cobalt ores from Canada, New Caledonia and 
Norway, which are the important producing countries, also 
nickel and cobalt ores from Oregon, Missouri and other minor 
localities. In the floor case opposite are larger examples of 
nickel ores and arsenic ores. This case also contains a series 
of minerals carrying aluminum in such form and quantity that 
it may be profitably extracted. These represent the present uni- 
versal aluminum ore, heauxite, and some minerals from which 
aluminum may be smelted in the near future. 
Clay, which is sporadically recommended as an aluminum 
ore, while it contains much aluminum, sometimes as much as 21 
per cent., has the metal present in such form that it cannot be 
economically extracted and is therefore not included among the 
ores of this metal. A collection of aluminum ores from all the 
important deposits of this metal as well as a series illustrating 
uses of the metal occupy the lower portions of this case. 
The following case contains tin ores. 
TIN. 
The common tin ore, is cassiterite, or oxide of tin, which 
carries 78.7 per cent, of tin, and the only other tin carrying min- 
eral of commercial importance, is stannite, sulphide of tin, iron 
and copper, with 17.5 per cent, of the metal. 
Tin ore from South Dakota, New South Wales, and Mexico, 
together with a nearly complete collection of the ores and rocks 
of the well known tin mines of Cornwall, which have been 
worked from the beginning of history. 
The process of reduction of tin ores to metal is illustrated 
by specimens from the Redruth Smelting Co., of Cornwall. 
Other examples of tin ore may be seen in the West Dome. 
Following the tin ore is a case of manganese ores. 
