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Formula: UO2
Simple oxide, uranium mineral, forms a series with thorianite
Pitchblende is a massive, often globular, possibly impure, variety of uraninite.
Specific gravity: 9.1 - 10.6
Hardness: 6
Streak: Black
Colour: Black, grey, brownish
Solubility: Slightly soluble in hydrochloric acid; moderately soluble in sulphuric and nitric acid
Common impurities: Th,Zr,Pb,Ra,Ac,Po,Ce,Y,Er,La
RADIOACTIVE
Environments:
Pegmatites
Hydrothermal environments
Uraninite occurs as a primary mineral in
granite and syenite
pegmatites, in high temperature hydrothermal veins and in
quartz pebble conglomerates
(Webmin).
In pegmatites uraninite is associated with zircon,
monazite,
tourmaline, mica and
feldspar
(HOM, Dana).
In hydrothermal veins it is associated with pyrite,
chalcopyrite, galena,
bismuth, silver,
nickeline, baryte,
fluorite and carbonates
(HOM).
At the Eldorado mine, Great Bear Lake, Northwest Territories, Canada, uraninite occurs in veins with native
silver
(Dana).
At the Shinkolobwe Mine, Shinkolobwe, Kambove District, Haut-Katanga, DR Congo, good specimens of sheet and wire
gold associated with uraninite have been
(R&M 96.3.220).
The type locality is Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic.
At Placeres de Guadalupe, Chihuahua, Mexico, uraninite occurs with gold
(Dana).
At the Longs Peak - St Vrain batholith near Jamestown, Jamestown District, Boulder county,
Colorado, USA, centimetre to decimetre sized mineralised pods and veins consist of zoned
mineral assemblages dominated by fluorbritholite-(Ce)
in a core 10 cm thick, with monazite-(Ce),
fluorite and minor quartz,
uraninite and sulphides. The core is surrounded by a
typically millimetre thick rim of allanite-(Ce), with
minor monazite-(Ce) in the inner part of the rim.
Bastnäsite-(Ce),
törnebohmite-(Ce) and
cerite-(Ce) appear in an intermediate zone between core and
rim, often just a few hundreds of microns wide
(R&M 96.3.252-253).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, uraninite has been found rarely in massive
microcline, commonly replaced by
schoepite-group minerals and other secondary uranium minerals. In the proximity of
uraninite, autunite and meta-autunite
are seen. The Emmons pegmatite is situated in a belt of metasedimentary rocks which originated as marine sediments which were
subsequently deformed and metamorphosed. The Emmons pegmatite is a highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.516).
At the pegmatites on Noyes Mountain, Greenwood, Oxford county, Maine, USA, uraninite is found
in a garnet layer in masses to 1.5 cm, associated with
coffinite and less commonly with autinite and
meta-autinite. Accessory zircon,
monazite and xenotime group species are intimately
associated with the uranium assemblage
(R&M 95.3.271).
At the the Chickering Mine, Walpole, Cheshire County, New Hampshire, USA, a single sample of uraninite has been found with
zircon in a pegmatite
(R&M 90.5.421).
At the Ruggles pegmatite, Grafton county, New Hampshire, USA, uraninite occurs intergrown with
albite-rich feldspar or with
muscovite, and associated
with smoky quartz, curite and
uranophane
(Dana, AM 23.334-341).
At Baringer hill, Llano county, Texas, USA, uraninite occurs in a pegmatite with gadolinite
(Dana).
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