Physics

Rhenium Definition Rhenium is a very rare, dense, silvery-white metallic element with a very high melting point. It is used to make catalysts and electrical…

Diorite Definition Diorite is a gray, coarse-grained plutonic rock. Diorite consists mainly of sodium-rich plagioclase and one or more mafic minerals such as biotite, hornblende,…

Monzonite Definition Monzonite is an igneous rock composed chiefly of plagioclase and orthoclase, with small amounts of amphibole, pyroxene, and biotite. Monzonite contains little or…

Syenite Definition Syenite is a light-colored, coarse-grained igneous rock consisting primarily of alkali feldspar together with some mafic minerals, especially hornblende. Unlike most igneous rocks,…

Chondrite Definition Chondrite is a stony meteorite that contains chondrules embedded in a fine matrix of the silicate minerals olivine and pyroxene. About 85 percent…

Meteorite Definition Meteorite is a meteor that reaches the Earth’s surface because it has not been burned up by friction with the atmosphere. Meteorites are…

Cryolite Definition Cryolite is a white or colourless mineral consisting of a fluoride of sodium and aluminium in monoclinic crystalline form: used in the production…

Fluorite Definition Fluorite (CaF2) is a transparent to translucent mineral occurring in many colors, especially yellow and purple, and usually in cube-shaped crystals with octahedral…

Pyrite Definition Pyrite (FeS2) is a silver to yellow, metallic, cubic mineral. Pyrite often crystallizes in cubes or octahedrons but also occurs as shapeless masses…

Tantalum Definition Tantalum is a hard, heavy, gray metallic element that is highly resistant to corrosion at low temperatures. It is almost immune to chemical…

Pyrochlore Definition Pyrochlore is a complex oxide mineral (Na,Ca)2Nb2O6(OH,F), which is composed of niobium, sodium, and calcium that forms brown to black, glassy octahedral crystals…

Niobium Definition Niobium is a smooth, silvery, ductile metallic component that, together with the element tantalum, typically occurs in nature. It is used for the…