Apatite

What is Apatite?
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 chemicals. 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. Those with good color and translucence are cut as cabochons.

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Physical Properties of Apatite
Fluorapatite: Ca5(PO4)3F Hydroxylapatite: Ca5(PO4)3(OH) Chlorapatite: Ca5(PO4)3Cl
 * Chemical Classification
 * Phosphate
 * Color
 * Green, brown, blue, yellow, violet, pink, colorless. Transparent specimens with excellent clarity and vivid color are used as gemstones.
 * Streak
 * White
 * Luster
 * Vitreous to subresinous
 * Diaphaneity
 * Transparent to translucent
 * Cleavage
 * Poor to indistinct
 * Mohs Hardness
 * 5
 * Specific Gravity
 * 3.1 to 3.3
 * Diagnostic Properties
 * Color, crystal form, and hardness. Brittle, often highly fractured. Can be scratched with a steel knife blade.
 * Chemical Composition
 * A group of calcium phosphates.
 * 5
 * Specific Gravity
 * 3.1 to 3.3
 * Diagnostic Properties
 * Color, crystal form, and hardness. Brittle, often highly fractured. Can be scratched with a steel knife blade.
 * Chemical Composition
 * A group of calcium phosphates.
 * Chemical Composition
 * A group of calcium phosphates.
 * A group of calcium phosphates.

Carbonate-rich apatite/francolite: Ca5(PO4,CO3)3(F,O)
 * Crystal System
 * Hexagonal
 * Uses
 * Fertilizer, phosphoric acid, hydrofluoric acid, gemstones, ore of rare earth elements, pigments, gemstone. Serves as a hardness of 5 on the Mohs Hardness Scale.
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 * Fertilizer, phosphoric acid, hydrofluoric acid, gemstones, ore of rare earth elements, pigments, gemstone. Serves as a hardness of 5 on the Mohs Hardness Scale.
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Physical Properties
Apatite is best known for its use as an index mineral with a hardness of 5 in the Mohs Hardness Scale. It is usually green in color, but can be yellow, brown, blue, purple, pink, or colorless. These colors are often so vivid that apatite has frequently been cut as a gemstone. Apatite is a brittle material. It breaks by both fracture and cleavage, but the cleavage is generally indistinct. Hexagonal apatite crystals are sometimes found in igneous and metamorphic rocks.