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Apatite

General Information

Apatite is three different minerals that vary depending on the predominance of fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen, although some specimens have been close to 100% of each these. The three are usually considered together due to the difficulty in distinguishing them in hand samples using ordinary methods.

Apatite is widely distributed in all rock types; igneous, sedimentary and metamorphic, but is usually just small grains or cryptocrystalline fragments. Large well formed crystals can be found in certain metamorphic rocks. Gem quality crystals of apatite can be cut, but the softness of apatite prevents wide distribution or acceptance of apatite as a gemstone
Chemistry: Ca5(PO4)3(OH F CL), Calcium (Flouro, Cloro, Hydroxyl) Phospate Class: Phosphates Group: Apatite Color: Green; can be Yellow, Blue, Purple, Reddish Brown Streak: White Luster: Vitreous to greasy
Transparency: Transparent to translucent Crystal System: Hexagonal Hardness: 5 Cleavage: Indistinct in basal direction Fracture: Conchoidial Specific Gravity: 3.1-3.2
Crystal Habits: Termination is typical hexagonal prism with the hexagonal pyramid or a pinacoid. Also accicular, granular, reniform and massive. Cryptocrystalline variety is called collophane and can make up a rock type called phosphorite. Can replace fossil fragments Uses: Phosphorus used in fertilizer and mineral specimens Associated Minerals: Hornblende, Mica, Nepheline, Calcite Other Characteristics: Unusual "partly disolved" look Notable Occurrences: Durango, Mexico; Bancroft, Ontario; Germany and Russia Best Field Indicators: Crystal habit, color, hardness and look
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