Apatite is the name of a group of phosphate minerals with similar chemical compositions and physical properties. They are an important constituent of phosphorite, a rock mined for its phosphorus content and used to make fertilizers, acids, and chemical. Apatite has a relatively consistent hardness and serves as the index mineral for a hardness of five in the Mohs Hardness Scale. Specimens with excellent clarity and color are sometimes cut as faceted gemstones.

The range of colors include colorless, pink, yellow, green, blue and violet. A rare variety is a rich purple from Maine. Blue Brazilian stones are second in demand. Madagascar is known to produce a neon blue-green material that is highly desirable. Light-green apatite carries the trade name 'asparagus stone'. The color of the best specimens of apatite can rival famed Paraiba tourmaline.

Chemical Formula: Ca5(PO4)3(F,Cl,OH); Color: Blue; Apatite group - Calcium fluoro-chloro-hydroxyl phosphate; Hardness: 5;