of the
two. Thus the carbonate has been dissolved out more rapidly, and in
addition descending waters carrying the phosphate have frequently
deposited it to pick up the carbonate. These enriching processes,
sometimes aided by mechanical concentration, have formed high-grade
deposits both in the originally phosphatic beds and in various
underlying strata. Concretionary and nodular textures are common. The
"pebble" deposits of Florida consist of the phosphatic materials broken
up and worked over by river waters and advancing shallow seas.

PYRITE

ECONOMIC FEATURES

The principal use of pyrite is in the manufacture of sulphuric acid.
Large quantities of acid are used in the manufacture of fertilizers from
phosphate rock, and during war times in the manufacture of munitions.
Sulphuric acid converts the phosphate rock into superphosphate, which is
soluble and available for plant use. Other uses of the acid are referred
to in connection with sulphur. Pyrite is also used in Europe for the
manufacture of paper from wood-pulp, but in the United States native
sulphur has thus far been exclusively used for this purpose. The residue
from the roasting of pyrite is a high-grade iron ore material frequently
very low in phosphorus, which is desirable in making up mixtures for
iron blast furnaces.

Most of the countries of Europe are producers of pyrite, and important
amounts are also produced in the United States and Canada. The European
production is marketed mainly on that continent, but considerable
amounts come to the United States from Spain.

Before the war domestic sources supplied a fourth to a third of the
domestic demand for pyrite. Imports came mainly from Spain and Portugal
to consuming centers on the Atlantic seaboard. The curtailment of
overseas imports of pyrite during the war increased domestic production
by about a third and resulted also in drawing more heavily on Canadian
supplies, but the total was not sufficient to meet the demand. The
demand was met by the increased use of sulphur from domestic deposits
(p. 109). At the close of the war supplies of pyrite had been
accumulated to such an extent that, with the prospect of reopening of
Spanish importation, pyrite production in the United States practically
ceased. War experience has demonstrated the possibility of substitution
of sulphur, which the United States has in large and cheaply mined
quantities. The future of the pyrite industry in the United Sta