Chlorapatit

Chlorapatite is a phosphate mineral in the apatite group with the chemical formula Ca5(PO4)3Cl. It represents the chloride-rich member of the apatite series, related to fluorapatite Ca5(PO4)3F and hydroxylapatite Ca5(PO4)3OH. The mineral crystallizes in the hexagonal system and commonly forms prismatic or tabular crystals, or granular aggregates.

The crystal structure is characteristic of the apatite group, with hexagonal symmetry and channels running along the c-axis that can host halogen ions such as chlorine. This composition reflects a substitution among the halogen/hydroxyl sites that distinguishes chlorapatite from the fluor and hydroxyl end-members.

Chlorapatite is typically colorless to white, but may appear pale green or brown in some specimens. It has a vitreous luster, a Mohs hardness of about 5, and a specific gravity near 3.1–3.2. It commonly occurs in igneous and metamorphic rocks as an accessory mineral and is often found in carbonatites and alkaline granites. It is frequently associated with fluorapatite, calcite, magnetite, and other phosphate minerals. Chlorapatite can form by crystallization from chlorine-rich fluids or by alteration of other apatite minerals.

In economic terms, chlorapatite can contribute to phosphate ore reserves and thus to fertilizer production, though fluorapatite is generally more abundant and economically significant in modern deposits. The mineral is of particular interest to mineralogists and petrologists as an indicator of fluid composition and phosphate mineralogy.