Oboniobite

oboniobite

fersmite

columbite

pyrochlore

Images

Formula: Mg₄Nb₂O₉
Oxide, niobium-bearing mineral
Crystal system: Trigonal
Specific gravity: 4.585 calculated
Colour: Yellowish brown to brown
Environments

Carbonatites

Oboniobite is a new mineral, approved in 2023 and to date (July 2025) reported only from the type locality.

Localities

At the type locality, the Bayan Obo deposit, Bayan Obo, Bayan Obo mining district, Baotou City, Inner Mongolia, China, oboniobite occurs in a dolomite-calcite carbonatite dike and is associated with fersmite, columbite, pyrochlore, apatite, magnetite, dolomite and calcite. Individual crystals range in size from 15 to 70 μm, and no twinning is observed. Oboniobite is yellowish brown to brown in colour and transparent, with a vitreous lustre.
Oboniobite shares a similar chemical composition with columbite-(Mg) and ternovite, yet it is notably different in its crystallographic, physical, and optical properties; it is not a variant of these two minerals; instead, it is a unique new mineral species that contains niobium and magnesium (AM 110.7.1094–1104).

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