Abuite, CaAl₂(PO₄)₂F₂, a new mineral from the Hinomaru–Nago mine, Yamaguchi Prefecture, Japan

Abstract

Abuite was found in hydrothermally altered rocks in the Hinomaru–Nago mine, Kiyo area, Abu, Abu County, Yamaguchi Prefecture, Japan (34°53′N 131°52′E). Abuite is often included in aluminum phosphate rich samples, embedded with quartz and augelite and/or trolleite, and is often accompanied by other phosphates especially apatite and crandallite. Abuite is transparent and colorless with white streak and vitreous luster. It is very difficult to find them in bare eyes, since the dominant phases in aluminum phosphate rich samples, augelite, trolleite, and quartz, are all also transparent and colorless. The empirical formula of abuite (based on 10 anions pfu, O = 8, F + OH = 2) is (Ca_0.99Sr_0.01)_1.00Al_1.96P_2.03O₈(F_1.89OH_0.11). H₂O was calculated by stoichiometry. The simplified formula is CaAl₂(PO₄)₂F₂. Abuite is the calcium analogue of SrAl₂(PO₄)₂F₂, which was synthesized by hydrothermal methods (Le Meins and Courbion, 1998). The crystal structure is orthorhombic, with space group P2₁2₁2₁. Unit cell parameters refined from the obtained X–ray diffraction pattern are a = 11.818(2), b = 11.993(3), c = 4.6872(8) Å and V = 664.3(2) ų, with Z = 4.