Calcium Chloroapatite

Description

Calcium chlorapatite, as a mineral, is relatively much rarer than fluorapatite or hydroxylapatite, and is formed primarily in F-deficient environments. It is found as a mineral in calcium silicate marble, is an accessory mineral in layered mafic intrusions, occurs in veins such as “Diabase” and replaces “Triphylite” in some granite pegmatites. Such deposits are found in the USA, Quebec in Canada, in the Bushveld complex of Transvaal, South Africa, at the Angarf-Sud Tazenakht Plain of Morocco, at Rajagarh, India, at Kurokura in Japan, and from Snarum, Norway.
Normally, calcium apatites are expected to be hexagonal. However, a nearly stoichiometric synthetic chloroapatite has been found to be pseudo-hexagonal with a monoclinic space group of P21/b and lattices parameters of a= 9.628?,b= 19.256?,c= 6.754?,γ= 120. The monoclinic and hexagonal forms are very similar, the most significant feature of the monoclinic structure being an ordered arrangements of the Cl^- ions above and below Z = 1/2 on the pseudo-hexagonal axis with the doubling of one cell dimension.