Abstract

The new mineral stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F [R3m, a = 7.0877(5) Å, c = 25.201(2) Å, V = 1096.4(1) Å3, Z = 3], belongs to the zadovite group, which also includes zadovite, BaCa6[(SiO4) (PO4)](PO4)2F; aradite, BaCa6[(SiO4)(VO4)](VO4)2F; and gazeevite, BaCa6(SiO4)2(SO4)2O. All minerals of this group exhibit single-layer antiperovskite modules, which are intercalated with tetrahedral layers. In stracherite, the first CO3-bearing intercalated hexagonal antiperovskite, about 38% of the (PO4)3– tetrahedra are randomly substituted by planar (CO3)2– groups. The mineral was discovered in spurrite rocks of the Hatrurim Complex in the Negev Desert near Arad, Israel. Associated minerals are spurrite, calcite, brownmillerite, shulamitite, CO3-bearing fluorapatite, fluormayenite-fluorkyuygenite, and ariegilatite. The empirical formula of stracherite is: (Ba0.96K0.02Na0.01)∑0.99Ca6.01[(SiO4)1.86 (PO4)0.12(AlO4)0.01(TiO4)0.01]∑2[(PO4)1.05(CO3)0.75(SO4)0.18(VO4)0.02]∑2(F0.95O0.03)∑0.98. Poikilitic crystals of stracherite are up to 0.5 mm in size and are confined to re-crystallization zones of spurrite marbles under the influence of by-products (gases, fluids) of combustion metamorphism.

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