tes
therefore looks cloudy, except for supplies used locally, as in the
territory tributary to the Great Lakes, and except for small amounts
locally recovered as by-products in the mining of coal or from ores of
zinc, lead, and copper. Pyrite production in the past has been chiefly
in the Appalachian region, particularly in Virginia and New York, and in
California.

GEOLOGIC FEATURES

Pyrite, the yellow iron sulphide, is the commonest and most abundant of
the metallic sulphides. It is formed under a large variety of conditions
and associations. Marcasite and pyrrhotite, other iron sulphide
minerals, are frequently found with pyrite and are used for the same
purposes.

The great deposits of Rio Tinto, Spain, which produce about half of the
world's pyrite, were formed by replacement of slates by heated solutions
from nearby igneous rocks. The ores are in lenticular bodies, and
consist of almost massive pyrite with a small amount of quartz and
scattered grains and threads of chalcopyrite (copper-iron sulphide).
They carry about 50 per cent of sulphur, and the larger part carries
about 2 per cent of copper which is also recovered.

Similar occurrences of pyrite on a smaller scale are known in many
places. Pyrite is very commonly found in vein and replacement deposits
of gold, silver, copper, lead, and zinc. In the Mississippi valley it is
extracted as a by-product from the lead and zinc ores, and in the
Cordilleran region large quantities of by-product pyrite could easily be
produced if there were a local demand. The pyrite deposits of the
Appalachian region are chiefly lenses in schists; they are of uncertain
origin though some are believed to have been formed by replacement of
metamorphosed limestones and schists.

Under weathering conditions pyrite oxidizes, the sulphur forming
sulphuric acid,--an important agent in the secondary enrichment of
copper and other sulphides,--and the iron forming the minerals hematite
and limonite in the shape of a "gossan" or "iron-cap."

Pyrite is likewise frequently found in sediments, apparently being
formed mainly by the reducing action of organic matter on iron salts in
solution. In Illinois and adjacent states it is obtained as a by-product
of coal mining.

SULPHUR

ECONOMIC FEATURES

Sulphur is used for many of the same purposes as pyrite. Under pre-war
conditions, the largest use in the United States was in the manufacture
of paper pulp by the sulphite process. Mi