Dzhuluite, Ca3SbSnFe3+3O12, a new bitikleite-group garnet from the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia

Dzhuluite, Ca3SbSnFe3+3O12 ( Ia 3 d , a = 12.536(3) A, V = 1970.05(9) A 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 (Ca2.954Fe2+0.043Mg0.003)∑3.000 (Sn0.850Sb5+0.764Zr0.121U6+0.127Ti4+0.070Sc0.009Nb5+0.058Hf0.001)∑2.001(Fe3+2.051Al0.653Fe2+0.182 Ti4+0.087Si0.028)∑3.001O12. 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 μm 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/cm3. 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.