| Botryoidal uraninite. Image taken from wikipedia commons here. |
A uranium-rich mineral with the formula UO2 (uranium oxide). Often, part of the uraninite is oxidized with the formula UO3. Uraninite is the primary ore for uranium and can also be mined for other elements such as radium, thorium, and lead, which are decay products of radioactive uranium. Uraninite deposits are generally a dark steel black with a slight metallic luster. The shape of uraninite is typically botryoidal (looks like a bunch of grapes) or amorphous, but rare cubic and octahedral crystals can form in certain environments. Uraninite often forms when hydrothermal circulation picks up uranium from a uranium-rich rock (such as granite or syenite) and concentrates this uranium in a hydrothermal ore deposit. The primary reason that uraninite is mined is to provide fuel for nuclear power plants.