Stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F, the first CO3-bearing intercalated hexagonal antiperovskite from Negev Desert, Israel

The new mineral stracherite, BaCa6(SiO4)(2)[(PO4)(CO3)]F [R (3) over barm, a = 7.0877(5) angstrom, c = 25.201(2) angstrom, V = 1096.4(1) angstrom(3), Z= 3], belongs to the zadovite group, which also includes zadovite, BaCa6(SiO4)(2)[(PO4)(PO4)(2)F; aradite, BaCa6(SiO4)(VO4)(VO4)(2)F; and gazeevite, BaCa6(SiO4)(2) (SO4)(2)O. 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, CO(3)(-)bearing fluorapatite, fluormayenite-fluorkyuygenite, and ariegilatite. The empirical formula of stracherite is: (Ba0.96K0.02Na0.01)(Sigma 0)Ca-.(99)6(.01)[(SiO4)(1.86)(PO4)(0.12)(AlO4)(0.01)(TiO4)(0.01)](Sigma 2)[(PO4)(1.05)(CO3)(0.75)(SO4)(0.)(18)(VO4)(0.02)](Sigma 2)(F0.95O0.03)(Sigma)(0.98). Poikilitic crystals of stracherite are up to 0.5 min in size and are confined to re-crystallization zones of spurrite marbles under the influence of by-products (gases, fluids) of combustion metamorphism.