The Rice has a great program called Adopt-a-Mineral, allowing the public to donate to the museum by adopting a rock and mineral. The following article is about one of those minerals, fluorite, available for adoption now.
Fluorite (AM 29, AM 30)
Carlo Galeani Napione named the mineral fluorite in the late 1700s. The name derives from the Latin “fleure”, meaning flow, because it is commonly used as a flux. Fluorite is a halide, in which a metal is bonded to one of the halogen elements (fluorine, chlorine, bromine, iodine).
The following images are used courtesy of Wiki Commons.
Fluorite is commonly translucent and found with a vitreous (glassy) luster. It has many colors including, green, purple, yellow, pink, brown and colorless. Its streak (color of the powdered mineral) is white. Fluorite has a hardness of ~4 and is the hardness reference species on Mohs’ scale. It is a brittle mineral, and it will fracture and break along perfect cubic and octahedral cleavage planes. Fluorite usually occurs as cubes, although it can also be found as octahedra (8-faced crystals), and rarely as dodecahedra (12-faced crystals). Sometimes these forms can be found combined in single crystals. When not seen as large crystalline specimens, fluorite is usu-ally massive, or an aggregate of very small cubes.
Fluorite is commonly fluorescent; in fact the term fluorescence was derived from the mineral. Under long-wave ultraviolet light, fluorite is usually blue, but it can fluoresce different colors, depending on the activators present. Certain colors are associated with specific localities, e.g. white fluorescent fluorite from Sterling Hill, New Jersey. Fluorite can also be phosphorescent.
Fluorite is a common mineral. It occurs in many geological settings, but most commonly as a gangue mineral in hydrothermal veins. It is commonly associated with lead and zinc minerals (e.g. galena and sphalerite). It can also be found in pegmatites.
Besides its use as a collector’s specimen, fluorite has many other uses, one of which includes the primary source of fluorine. As mentioned above, fluorite is used as a flux when manufacturing steel. Fluxing involves the addition of fluorite to improve flow and prevent the formation of oxides thus eliminating impurities. Fluorite can also be used in optics for making lenses. Given its relative softness, it is also used for carvings, particularly in China.
There are many classic localities worldwide for fluorite. The most noteworthy places include Durham County, England, Chamonix, France, and Dal’negorsk, Russia. In the USA, Hardin County, Illinois has produced many beautiful specimens, as has Smith County, Tennessee. China has become a wonderful producer of fine fluorite specimens.