Formula: UO2
Simple oxide, uranium mineral, forms a series with thorianite
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

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).

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 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).

Common impurities: Th,Zr,Pb,Ra,Ac,Po,Ce,Y,Er,La

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