Abstract

Garnet from an aposkarn achtarandite-bearing rodingite-like rock in Sakha-Yakutia, Russia, has a Sc content close to 6 wt% Sc2O3 (~0.45 apfu). The scandian garnet is a relict mineral from a high-temperature, shallow-level melilite skarn. Structural and electron microprobe data for a crystal of the scandian garnet with cell parameter a = 12.331(1) Å, Iad allows refinement of the structural formula (Ca2.97Mg0.02Y0.01)∑3(Fe3+0.663Zr0.584Ti4+0.294Sc0.153Cr0.152Mg0.094Fe2+0.04Hf0.008V0.003)∑2(Si1.898Al0.420Ti4+0.359 Fe3+0.323)∑3O12. Investigation of the composition of many of the scandian garnets reveals the existence of a solid-solution between kimzeyite-schorlomite Ca3(Zr,Ti)2(Al,Fe)2SiO12 and the scandium analog of andradite Ca3Sc2Si3O12. This is the first report of a natural scandian garnet.

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