gsten, but it is more difficult to control metallurgically.
It has been used in piston rods and crank shafts for American
airplanes. Its use in tool steel is mainly confined to Europe, where its
metallurgical application is in a more advanced stage than in the United
States. Molybdenum is added to steel either as powdered molybdenum or in
the form of ferromolybdenum, an alloy containing 60 to 70 per cent of
the metal. Molybdenum chemicals are essential reagents in iron and steel
analysis and other analytical work; they are also used as pigments.
Molybdenum metal has been used to a small extent in incandescent lamps
and as a substitute for platinum in electric contacts and resistances.

Molybdenum ores range from considerably less than 1 per cent to about 5
per cent in molybdenum.

The world's principal sources of molybdenum ores in approximate order of
importance are the United States, Canada, Norway, Australia, Korea,
Austria, Peru, and Mexico.

About half of the world's supply is produced in the United States.
Production of molybdenum in this country practically began in 1914. Most
of the production has come from Colorado and Arizona. It is believed
that the United States contains reserves more than sufficient to meet
any possible future demand. Thus far the demand has not kept up with
capacity for production. The principal consuming countries are England,
France, and Germany.

GEOLOGIC FEATURES

The chief ore minerals are molybdenite (molybdenum sulphide) and
wulfenite (lead molybdate). The larger part of the world's production is
from the molybdenite ores. Molybdenite occurs principally in association
with granitic rocks,--in pegmatite dikes, in veins, and in
contact-metamorphic deposits,--in all of which associations its origin
is traced to hot solutions from the magma. It is frequently present as
an accessory mineral in sulphide deposits containing ores of gold,
copper, silver, lead, and zinc. At Empire, Colorado, one of the
principal producing localities, it is found in veins, associated with
pyrite, and filling the interstices between brecciated fragments of a
wall rock composed of alaskite (an acid igneous rock). In molybdenite
deposits secondary concentration has not been important.

Wulfenite is rather common in the upper oxidized zone of deposits which
contain lead minerals and molybdenite. It is probably always secondary.
Deposits of wulfenite have been worked on a small scale in Arizona.

VANAD