Nioboixiolite-([])

nioboixiolite-([])

zircon

actinolite

columbite-(Fe)

Images

Formula: (Nb_0.8◻_0.2)⁴⁺O₂
Oxide, ixiolite group, columbite supergroup, niobium-bearing mineral
Crystal system: Orthorhombic
Specific gravity: 6.05 calculated
Hardness: 6 to 6½
Streak: Black
Colour: Grey to deep black
Luminescence: Not fluorescent under UV
Environments

Carbonatites

Nioboixiolite-([]) is a new mineral, approved in 2022 and to date (May 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, nioboixiolite-([]) occurs as anhedral to subhedral grains 100 to 500 µm across, disseminated in carbonatite rock composed of dolomite, calcite, magnetite, apatite, biotite, actinolite, zircon and columbite-(Fe). Most of these grains are highly serrated, with numerous inclusions of columbite-(Fe). Minerals associated with nioboixiolite-([]) include magnetite, pyrite, dolomite, apatite, zircon, actinolite and columbite-(Fe) (Mindat).

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