Physics

Gallium Definition Gallium is a rare, silvery metallic element that is found as a trace element in coal, in bauxite, and in several minerals. It…

Mercury Definition Mercury is a silvery-white, dense, poisonous metallic element that is a liquid at room temperature and is used in thermometers, barometers, batteries, and…

Uranium Definition Uranium is a heavy, silvery-white, highly toxic, radioactive metallic element of the actinide series. It has 14 known isotopes, of which U 238…

Erbium Definition Erbium is a soft malleable silvery-white element of the lanthanide series of metals: used in special alloys, room-temperature lasers, and as a pigment.…

Xenotime Definition Xenotime is a phosphate mineral, similar to monazite except enriched in the heavy lanthanides and yttrium. It is a rare earth phosphate mineral.…

Terbium Definition Terbium is a soft, silvery-gray metallic element of the lanthanide series. It is used in color television tubes, x-ray machines, and lasers. Its…

Gadolinium Definition Gadolinium is a silvery-white, malleable, ductile metallic element of the lanthanide series that has seven natural isotopes and 11 artificial isotopes. It is…

Limonite Definition Limonite is a common brown, black, or yellow amorphous secondary mineral that consists of hydrated ferric oxides and is a source of iron.…

Allanite Definition Allanite is a rare black or brown mineral consisting of the hydrated silicate of calcium, aluminium, iron, cerium, lanthanum, and other rare earth…

Tanzanite Definition Tanzanite is the violet to blue form of the mineral zoisite.  It is a calcium alumina hydroxy silicate. The gemstone was discovered by…

Zoisite Definition Zoisite is a grayish or whitish mineral occurring in orthorhombic, prismatic crystals, also in columnar masses. It is a silicate of alumina and…

Epidote Definition Epidote is a yellowish-green or blackish-green monoclinic mineral. Epidote occurs as formless grains or as prism-shaped crystals, and is found in limestones that…