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PYRITE. 
Pyrite or iron pyrites is a yellow mineral of metallic lustre 
consisting of the disulphide of iron, FeS 2 . It occurs in massive 
form or as crystals, usually of cubic or octahedral habit. When 
pure it contains 46-6 per cent of iron and 53-4 per cent of 
sulphur. 
Pyrite is one of the most widely distributed minerals, 
occurring in rocks of every type and age. It is also a common 
vein mineral, in some cases constituting practically the entire 
vein matter. 
USES. 
The main use of pyrite is as a source of sulphur in the manu 
facturing of sulphuric acid. The mineral is roasted in an oxidiz 
ing atmosphere, in specially designed furnaces. The sulphur 
content burns to sulphur dioxide (SO2), and the iron to ferric 
oxide (Fe 2 0 3 ). The gaseous sulphur dioxide is further treated 
to convert it into the trioxide (SO3), which on taking up water 
becomes sulphuric acid (H2SO4). The ferric oxide which is 
the solid product of the roasting process, often spoken of as 
pyrite residue or cinder, is of the same composition as hematite. 
It is frequently smelted for its iron content, or, if the original 
pyrite contained copper, gold or silver values, these metals may 
be extracted by smelting or some other metallurgical process. 
The pyrite residue is used also for making paint. It is a bril 
liant red and makes the pigment known as red oxide or Indian 
red. The residue from a well roasted pyrite contains about 
one-half a per cent of sulphur. 
In his report on pyrites, 1 Dr. Wilson states that "pyrites 
suitable for acid making should contain as much sulphur as 
possible The greater number of acid makers demand 
a product containing not less than 42 per cent sulphur; there are, 
1 “ Pyrites in Canada,” by Dr. A. W. G. Wilson, Report No. 167, Mines Branch. 
This report deals in detail with the subject of pyrite, its occurrence in Canada, the 
methods of exploitation, dressing, and its uses. There are chapters on sulphuric acid making 
and the use of pyrite in the pulp industry.