m plants in the United States
capable of producing annually from domestic ores an amount several times
as large as the entire production of the rest of the world. Practically
all the production has come from Colorado and Utah. Known reserves are
not believed to be sufficient for more than a comparatively few years'
production, but it is not unlikely that additional deposits will be
found in the same area.

GEOLOGIC FEATURES

Uranium is one of the rarer metals. Radium is found only in uranium ores
and only in exceedingly small quantities. The maximum amount which can
be present in a state of equilibrium is about one part of radium in
3,000,000 parts of uranium. The principal sources of uranium and radium
are the minerals carnotite (hydrous potassium-uranium vanadate) and
pitchblende or uraninite (uranium oxide).

The deposits of Joachimsthal, Bohemia, contain pitchblende, along with
silver, nickel, and cobalt minerals and other metallic sulphides, in
veins associated with igneous intrusions.

The important commercial deposits of Colorado and Utah contain
carnotite, together with roscoelite (a vanadium mica) and small amounts
of chromium, copper, and molybdenum minerals, as impregnations of
flat-lying Jurassic sandstones. The ores carry up to 35 per cent uranium
oxide (though largely below 2 per cent), and from one-third as much to
an equal amount of vanadium oxide. The ore minerals are supposed to have
been derived from a thick series of clays and impure sandstones a few
hundred feet above, containing uranium and vanadium minerals widely
disseminated, and to have been carried downward by surface waters
containing sulphates. The ore bodies vary from very small pockets to
deposits yielding a thousand tons or so, and are found irregularly
throughout certain particular beds without any special relation to
present topography or to faults. The association of many of the deposits
with fossil wood and other carbonaceous material suggests that organic
matter was an agent in their precipitation, but the exact nature of the
process is not clear. In a few places in Utah the beds dip at steep
angles, and the carnotite appears in spots along the outcrops and
generally disappears as the outcrops are followed into the hillsides;
this suggests that the carnotite may be locally redissolved and carried
to the surface by capillary action, forming rich efflorescences. Because
of the nature of the deposits no large amount of ore is deve