Formula: (Y,REE,Ca,Th,Fe)(Nb,Ti,Ta)2(O,OH)6
Multiple oxides, aeschynite group
Specific gravity: 5.34
Hardness: 5 to 6
Streak: Greyish brown
Colour: Deep brownish red
Common impurities: Fe,Ta
Environments
Nioboaeschynite-(Y) occurs in calcite veins in regionally metamorphosed metasedimentary rocks
that may have undergone fenitisation - like metasomatism. Associated minerals include
fluorapatite, amphibole,
titanite, anorthite,
microcline, annite,
calcite, quartz,
monazite, pyrite and uranium-rich
thorite
(HOM).
Localities
At the nioboaeschynite-(Y) type locality, the Bear Lake diggings, Monmouth Township, Haliburton County, Ontario, Canada,
nioboaeschynite-(Y) occurs in calcite veins as subhedral crystals to 1 cm, in association
with apatite, amphibole,
feldspar, biotite,
calcite, quartz,
monazite, pyrite and uranium-rich
thorite
(CM 46.2.395-402).
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