Eringaite, Ca3Sc2(SiO4)3, a new mineral of the garnet group

Abstract

AbstractEringaite, Ca3Sc2(SiO4)3, a new mineral of the garnet group, is an accessory mineral in metasomatic rodingite-like rocks from the Wiluy River, Sakha-Yakutia Republic, Russia. Eringaite forms regular growth zones and irregular spots in complex garnet crystals containing a kimzeyite core. An electron back-scatter diffraction pattern with an excellent match to a garnet model with a = 12.19 Å was obtained for a grain with the largest Sc2O3 content having the crystal chemical formula (Ca2.98Y0.01Mg0.01)Σ3(Sc0.82Ti4+0.44Fe3+0.30Zr0.21Mg0.10Al0.09Cr3+0.08Fe2+0.05V3+0.01)Σ2.01(Si2.48Al0.30Fe3+0.22)Σ3O12. Eringaite is light brown to yellow with a creamy white streak. The crystals are transparent with a vitreous lustre. The calculated density of eringaite is 3.654 g cm–3. The following main modes of the Raman spectrum are characteristic of eringaite: 335, 511, 735, 880 and 937 cm–1. The strongest lines of the calculated powder diffraction data are as follows [(hkl) dhkl (I)] (400) 3.064 (69), (420) 2.740 (100), (422) 2.502 (68), (640) 1.670 (30), (642) 1.638 (82), (840) 1.370 (20), (842) 1.137 (19), (10.4.2) 1.119 (29).