Dzhuluite, Ca (sub 3) SbSnFe (super 3+) (sub 3) O (sub 12) , a new bitikleite-group garnet from the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia

Dzhuluite, Ca (sub 3) SbSnFe (super 3+) (sub 3) O (sub 12) (Ia3d, a = 12.536(3) Aa, V = 1970.05(9) Aa (super 3) , Z = 8), a new antimony garnet of the bitikleite-group, was discovered in a kumtyubeite zone in close proximity to the contact with unaltered ignimbrite in a skarn xenolith from the Upper Chegem Caldera, Northern Caucasus, Russia. The empirical formula of the holotype dzhuluite is (Ca (sub 2.954) Fe (super 2+) (sub 0.043) Mg (sub 0.003) ) (sub Sigma 3.000) (Sn (sub 0.850) Sb (super 5+) (sub 0.764) Zr (sub 0.121) U (super 6+) (sub 0.127) Ti (super 4+) (sub 0.070) Sc (sub 0. 009) Nb (super 5+) (sub 0.058) Hf (sub 0.001) ) (sub Sigma 2.001) (Fe (super 3+) (sub 2.051) Al (sub 0.653) Fe (super 2+) (sub 0.182) Ti (super 4+) (sub 0.087) Si (sub 0.028) ) (sub Sigma 3.001) O (sub 12) . Associated minerals are kumtyubeite, cuspidine, fluorchegemite, larnite, fluorite, wadalite, rondorfite, hydroxylellestadite, perovskite, lakargiite, kerimasite, elbrusite, srebrodolskite, bultfonteinite, ettringite group minerals, hillebrandite, afwillite, tobermorite-like minerals, hydrocalumite and hydrogrossular. Dzhuluite forms poikilitic crystals <50 mu m in size that are light-yellow to dark-brown and with a creamy streak. The lustre is strongly vitreous. The calculated density of dzhuluite ranges from 4.708 to 4.750 g/cm (super 3) . Raman spectra are analogous to those of kimzeyite, kerimasite and other bitikleite-group minerals. Dzhuluite formed at high temperature during a retrograde stage of primary rock alteration in the larnite subfacies (sanidinite facies) as a result of fluorine metasomatism.