Formula: Ca5(PO4)3Cl
Anhydrous phosphate containing halogen, apatite group, apatite supergroup
Crystal System: Hexagonal
Specific gravity: 3.17 to 3.18 measured, 3.17 calculated
Hardness: 5
Streak: White
Colour: White
Solubility: Soluble in hydrochloric acid or in nitric acid

Metamorphic environments
Hydrothermal environments

Chlorapatite is relatively much rarer than fluorapatite or hydroxylapatite, formed in F-deficient environments. In calc-silicate marble; an accessory mineral in layered mafic intrusions; in veins through dolerite; replacing triphylite in granite pegmatites; in meteorites (HOM). A monoclinic polymorph, chlorapatite-M is known.
Common associates include hornblende, ilmenite, magnetite, pyrrhotite, rutile, scapolite and titanite (Mindat).


At the Bobs Lake Chlorapatite occurrence, Oso Township, Frontenac County, Ontario, Canada, the area of chlorapatite occurrence consists mainly of granites, granitic gneisses and gneissic granodiorites with some anorthositic gabbros. Interfingering with the granitic rocks are irregular bands of amphibolite and marble. Most of the skarn deposits in the area are of the phlogopite - fluorapatite type occasionally with considerable quantities of scapolite.
The chlorapatite at Bob's Lake occurs in calc-silicate marble as a thin vein. The apatite is associated with actinolite, diopside and lesser amounts of calcite, quartz and talc. The vein minerals with the exception of the chlorapatite also occur in the surrounding marble. Mica and scapolite are noticeably absent. Talc coats much of the actinolite and occurs as inclusions in the calcite and apatite. In some cases the calcite has weathered to a rhombohedral framework of talc.
In general the chlorapatite crystals are pinkish-white and have a chalky lustre due to the included talc, some crystals observed have a thin chalky coating and transparent cores. Completely transparent, pale yellow crystals have also been found but these are not very common (CM 10.252–259).

At the Angarf-South pegmatite, Ouisselsate Caïdat, Amerzgane Cercle, Ouarzazate Province, Drâa-Tafilalet Region, Morocco, chlorapatite is associated with olivine, orthopyroxene, phlogopite, ferroalluaudite and chromite (HOM).

There are two co-type localities, Kragerø, Vestfold og Telemark, Norway and Diksberg, Ransäter, Munkfors, Värmland County, Sweden.
At the type localities chlorapatite occurs as white hexagonal crystals associated with titanite, rutile, ilmenite, calcite and albite (Mindat).

At the Fairfax quarry, Centreville, Culpeper Basin, Fairfax county, Virginia, USA, apatite group crystals are zoned with the crystal cores consisting of translucent light greenish-grey chlorapatite and opaque white alteration zones of fluorapatite along the crystal margins and internal fractures.
A paragenetic sequence is suggested in which, after precipitation of chlorapatite and diopside along a joint in the dolerite, the host rock and the chlorapatite crystals were fractured and then altered by a fluorine-containing solution that partially replaced the chlorine, thus producing the zoned crystals. (R&M 98.2.126).

At the Bull Run Quarry, Conklin, Loudoun county, Virginia, USA, chlorapatite is associated with amphibole, chlorite, plagioclase, titanite and datolite (HOM).

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