Calcium Phosphate Fluoride Hydroxide Chloride, Ca5(PO4)3(F,OH,Cl)
Crystal System: Hexagonal
Hardness: 5.0
Density: 3.16-3.22

Apatite is a group name, applied to phosphates, arsenates and vanadates. It's members are the most common of the phosphorus-bearing minerals. The group members are differentiated on the basis of their predominant anions i.e. fluorapatite (FL), hydroxylapatite (OH), or chloroapatite (CL). Apatites are formed under a variety of conditions but most commonly occur as accessory minerals in igneous rocks. They also occur in marine sedimentary rocks formed by chemical deposition, in fossils, and in metamorphic rocks.

Apatites vary widely in color from colorless to yellow, green, brown, red and blue. Some apatites display a yellow fluorescence under ultraviolet light. Group members exhibit hexagonal, prismatic crystals which may be stubby to elongated and are often terminated by dipyramidal faces.

Rocks from Martin Friedlander's Collection

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bkeller@rockhounds.com 8/5/95