Uraninite
Uraninite is a radioactive, uranium-rich mineral and the most important ore of uranium. Chemically, it is largely uranium dioxide (UO2), but because of oxidation, it typically contains variable proportions of uranium trioxide (UO3). It also commonly contains thorium, radium, lead, and other elements. The lead present is largely radiogenic, a product of the radioactive decay of uranium.
Uraninite is typically black or brownish-black in color, with a metallic or submetallic luster. Its hardness ranges from 5 to 6 on the Mohs scale, and its specific gravity is very high, ranging from approximately 7 to 10 or higher depending on composition.
The crystal structure of uraninite is isometric, though well-formed crystals are rare. It more commonly occurs in massive or botryoidal forms. Uraninite is strongly radioactive due to the presence of uranium and its decay products.
Occurrence: Uraninite is found in a variety of geological settings, including pegmatites, hydrothermal veins, and sedimentary rocks. Important deposits are found in Canada, the Democratic Republic of the Congo, Australia, and the United States (Colorado Plateau).
Uses: The primary use of uraninite is as a source of uranium for nuclear fuel and for the production of radioisotopes. Historically, it was also used as a coloring agent in ceramics and glass, although this is now rare due to its radioactivity.
Associated Minerals: Uraninite is often found associated with other uranium minerals, such as coffinite, autunite, and torbernite, as well as with minerals like quartz, feldspar, and various sulfides.
Safety Precautions: Due to its radioactivity, uraninite should be handled with care. Proper shielding and ventilation are necessary when working with uraninite to minimize exposure to radiation.