Nioboaeschynite

minerals

aeschynite

monazite-(Ce)

thorite

Formulae:
nioboaeschynite-(Ce): (Ce,Ca)(Nb,Ti)2(O,OH)6
nioboaeschynite-(Y): (Y,REE,Ca,Th,Fe)(Nb,Ti,Ta)2(O,OH)6
Multiple oxides, aeschynite group
Specific gravity: nioboaeschynite-(Ce) 5.04 nioboaeschynite-(Y) 5.34
Hardness: nioboaeschynite-(Ce) 5½ nioboaeschynite-(Y) 5 to 6
Streak: nioboaeschynite-(Ce) Brown nioboaeschynite-(Y) Greyish brown
Colour: nioboaeschynite-(Ce) Black, dark red nioboaeschynite-(Y) Deep brownish red
Common impurities: nioboaeschynite-(Y) Fe,Ta
Environments

Metamorphic 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).

At the nioboaeschynite-(Ce) type locality, the Vishnevye Mountains, Chelyabinsk Oblast, Russia, At the nioboaeschynite-(Ce) occurs in quartz - arfvedsonite veinlets cutting fenite associated with quartz and arfvedsonite (HOM, Dana).

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