Aeschynite-(Y)

minerals

allanite

monazite-(Ce)

thorite

Formula: (Y,Ln,Ca,Th)(Ti,Nb)2(O,OH)6 most common
Multiple oxide containing niobium or titanium, aeschynite group, forms series with aeschynite-(Ce) and with tantalaeschynite-(Y) (Mindat).
Specific gravity: 4.82 to 4.93
Hardness: 5 to 6
Streak: White, pale yellow, reddish yellow
Colour: Pale yellow, yellow-orange, pale greenish yellow, black, brownish black
Solubility: Insoluble in hydrochloric acid, and soluble in HF or in a fusion with KHSO4 (Dana).
Environments

Plutonic igneous environments
Pegmatites
Carbonatites
Placer deposits
Metamorphic environments

Aeschynite-(Y) occurs in granite and granite pegmatites, in ankerite-dolomitic carbonatites and as a detrital mineral in placers. Associated minerals include euxenite, monazite, xenotime, allanite, zircon, fergusonite, thorite, synchysite, gadolinite, chernovite-(Y), columbite, biotite, muscovite, titanite and corundum (HOM, Mindat).

Localities

In South China aeschynite-(Y) occurs in an yttrium-rare-earth-rich muscovite granite, associated with xenotime, monazite, zircon, fergusonite, thorite, synchysite-(Y), gadolinite, chernovite-(Y), columbite and cassiterite (AM 61.178, Dana).

At the Trimouns quarry, Luzenac, Ariege, France, aeschynite-(Y) is found in the talc - chlorite mineralisation zone, filling dolomite vugs commonly associated with calcite. Some aeschynite crystals are sprinkled with limonitised pyrite (MinRec 35.3.231-232).

At the type locality, the Urstad Feldspar Mine, Hidra, Flekkefjord, Norway, aeschynite-(Y) occurs in a granite pegmatite.

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