Apatite is actually not a single mineral, but a phosphate mineral group consisting of Chlorapatite, Fluorapatite, and Hydroxylapatite. Each individual mineral has a certain level of chlorine, fluorine, or hydroxy in varying amounts and combinations. The most common gem variety is a translucent to transparent semiprecious gemstone that is steadily increasing in popularity within the jewelry trade. Apatite is found in igneous, metamorphic, and sedimentary rock with large crystals being found primarily in metamorphic rock.
Apatite displays strong fluorescence under short wave ultra-violet light. There is a particularly intense and deeply saturated, geenish-blue (aka swiss blue) variety from Madagascar known as "Neon Apatite" that is becoming quite popular in the gem trade. Dark yellowish-green varieties are sometimes referred to as "asparagus stone." The name "Apatite" is derived from the Greek word "apate" meaning "deceit" or "to deceive."
Gemmy apatite crystals can be facet cut but the softness lends itself to be cut en cabochon. Chatoyant varieties of apatite are typically cut into a cabochon. Hydroxylapatite is the major component of tooth enamel, and Fluorapatite (aka fluoroapatite) is used in fluoridated water to help strengthen teeth by exchanging hydroxyl ions for fluoride ions.
Apatite is one of the softer faceted gemstones, with a mineral hardness of only 5 on the Mohs scale, and apatite can be acid and heat-sensitive. Apatite crystalizes in the hexagonal crystal system, and has a hexagonal prism or hexagonal pyramid crystal habit with pinacoid terminations.
Apatite has a refractive index of 1.63 to 1.64 and a vitreous surface luster. Basal cleavage is indistinct.
Chemical composition: Ca5(PO4)3 (OH, F,Cl)
Semi-Precious Stones