bsorbing normally nearly one-half of the world's
production. Approximately three-fifths of this consumption is in the
form of mica splittings, most of which are made from muscovite in India
and part from amber mica in Canada. Due to the cheapness of labor in
India and the amenability of Indian mica to the splitting process, India
splittings should continue to dominate the market in this country. Amber
mica is a variety peculiarly adapted to certain electrical uses. There
are no known commercial deposits of this mica in the United States, but
American interests own the largest producing mines in Canada. Shipments
of Brazilian mica are not of such uniformly high quality as the Indian
material, but promise to become of increasing importance in American
markets.

Of the sheet mica consumed annually, the United States normally produces
about one-third. War conditions, although stimulating the production of
domestic mica very considerably, did not materially change the
situation in this country as regards the dependence of the United States
on foreign supplies for sheet mica.

About 70 per cent of the domestic mica comes from North Carolina and 25
per cent from New Hampshire. The deposits are small and irregular, and
mining operations are small and scattered. These conditions are largely
responsible for the heterogeneous nature of the American product. It is
hardly possible for any one mine to standardize and classify its
product, although progress was made in this direction during the war by
the organization of associations of mica producers. This lack of
standardization and classification is a serious handicap in competition
with the standard grades and sizes which are available in any desired
amounts from foreign sources.

For ground mica, the domestic production exceeds in tonnage the total
world production of sheet mica, and is adequate for all demands.

GEOLOGIC FEATURES

Mica is a common rock mineral, but is available for commerce only in
igneous dikes of a pegmatite nature, where the crystallization is so
coarse that the mica crystals are exceptionally large. Muscovite mica
occurs principally in the granitic pegmatite dikes. The phlogopite mica
of Canada occurs in pyroxenite dikes. The distribution of mica within
the dikes is very erratic, making predictions as to reserves hazardous.
The associated minerals, mainly quartz and feldspar, are ordinarily
present in amounts greater than the mica. Also, individual de