Abstract

Eringaite, 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(SC0.82

\(\mathrm{Ti}_{0.44}^{4+}\)
\(\mathrm{Fe}_{0.30}^{3+}\)
Zr0.21Mg0.10Al0.09
\(\mathrm{Cr}_{0.08}^{3+}\)
\(\mathrm{Fe}_{0.05}^{2+}\)
\(\mathrm{V}_{0.01}^{3+}\)
)Σ2.01(Si2.48Al0.30
\(\mathrm{Fe}_{0.02}^{3+}\)
)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).

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