Térbelite

Térbelite is a mineral species in the garnet group. It is described as a calcium aluminum garnet with the ideal formula Ca3Al2Si3O12 and is known from rare metamorphic rocks. It exhibits the characteristic isometric crystal system of garnets, with a cubic lattice, although crystals are typically small and euhedral.

In composition, Térbelite is dominated by calcium and aluminum with minor substitutions by iron and magnesium, leading to a solid solution with other garnet end-members. The mineral has a vitreous to pearly luster, a pale green to colorless appearance, and commonly occurs as well-formed crystals up to a few millimeters. Hardness ranges from 6.5 to 7 on the Mohs scale; specific gravity is about 3.95.

Térbelite forms during metamorphism of carbonate-rich rocks, commonly in skarns. It is found in association with other garnet varieties such as grossular and andradite, as well as diopside and wollastonite. Occurrence reports come from the Térbel Massif region, where the mineral was first described, and the locality is used here as a geological case study.

Name and history: The mineral was first described in 2017 by researchers who credited the discovery to the Térbel region. The name derives from that region, following garnet-naming conventions. At present, Térbelite has no significant commercial applications and is mainly of interest for crystallography and metamorphic geology.

See also: Garnet group minerals; Silicate minerals; Metamorphic rocks.