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Carnotite Mineral Facts:
Chemical Formula:
K2(UO2)2(VO4)2-3H2O
Carnotite, like the other uranites, is extremely complex in composition.
Carnotite is a vanadate of uranium and potassium, with variable amounts
of water and a number of common
impurities including calcium, barium, magnesium, iron, and sodium.
Colors:
Characteristic bright yellow color
from the Uranyl ion.
Hardness:
2
Density:
about 4.2
Cleavage:
Perfect basal cleavage
Its cleavage is very perfect parallel to (00I).
Crystallography: Monoclinic
The mineral has been found only in tiny crystalline grains, so that its
crystalline properties are not easily observed. Even small crystals are
rare.
Luster:.
Earthy
luster normal.
Earthy to dull, clay-like texture
in most specimens, some specimens can appear pearly.
Optics:
(Refractive Index): a= 1.75 to 1.78
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Composition,
Structure and Associated Minerals:
Carnotite is a secondary mineral resulting from the solution
and deposition of various uranium containing minerals. It is the most
important uranium ore in the USA. It is mined from occurrences in where
water flowed underground through sandstones, especially in paleochannels,
near fossil carbonaceous matter, in calcretes and near playas.
Carnotite occurs as a yellow crystalline powder, some of which seems to
consist of minute crystals with an hexagonal habit, in the interstices
between the grains in sandstones and conglomerates, as nodules or lumps in
these rocks, and as coatings on the walls of cracks in pebbles in the
conglomerates and as impregnations on pieces of silicified wood
embedded in the sandstones. It is limited to very shallow depths and is
apparently nearly always deposited from ground waters.
Identification and Diagnostics
It is is
identified from its bright yellow in color, radioactivity and the presence
of vanadium. It is completely soluble in HNO3 . If to the nitric acid
solution hydrogen peroxide be added, a brown color will appear. Or if the
solution is filtered, made alkaline by ammonia and through it is passed H2S
a garnet color will develop. If the mineral be moistened by a drop of
concentrated HC1, a rich brown color will result. The addition of a drop or
two of water will change the color to light green or make it disappear.
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Occurrence,
Localities and Origins:
Its principal known
occurrences are in the western part of the USA. Productive locations where
carnotite has been mined include Montrose, San Miguel, Mesa and Dolores
Counties in southwestern Colorado, especially in Paradox Valley, and in the
adjoining portions of New Mexico and Utah, and in Rio Blanco and Routt
Counties in the northwestern portion of Colorado. At all these places there
are large quantities of the impregnated rock which remain but it contains on
the average only about 1.5 per cent to 2 per cent of Uranium. Historically,
Carnotie has been mined both from surface and underground operations, but at
present is only mined using in-situ solution methods. The mineral has also
been described from Arizona, Mt. Pisgah, Mauch Chunk, Pennsylvania, and from
Radium Hill, South Australia.
The mineral is one of the main sources of uranium and is one of the
principal sources of vanadium - these ores were once worked chiefly
for their radium content at a time when few sources of intense radioactivity
were known. Uranium is used chiefly for nuclear fission applications, both
for peaceful power generation and as a weapon. This metal depleted of
its U235 (fissionable form) is used to some extent in making bulletproof
insulation panels for tanks and other infantry vehicles (depleated uranium).
Uranium was once used in the manufacture of pottery, iridescent glazes and
glass, though for health and safety reasons this is no longer done because
of residual radioactivity. The uses of vanadium are mostly related to the
steel industry. The principal value of carnotite depends upon its content of
uranium, and for decades carnotite was the principal source of the world's
uranium. Practically the only other commercial source in the US is the
pitchblende of Gilpin, Colorado. Carnotite has been mined in San Miguel and
Montrose Counties, Colorado, and at several points in eastern Utah, but
mainly for the vanadium it contains.
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