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).
Crystal System: Orthorhombic
Specific gravity: 4.82 to 4.93 measured, 5.5 calculated
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).
Aeschynite-(Y) from Trimouns - Image
At the Monte Cervandone area, Devero Alp, Baceno, Verbano-Cusio-Ossola Province, Piedmont, Italy, red to dark brown
to almost black, tabular crystals of aeschynite-(Y) to almost 1 cm are found on both the Swiss and Italian
sides of Cervandone; the crystals are non-metamict and commonly lustrous. Fine elongated tabular aeschynite-(Y)
crystals to 7 mm, dark red-brown and transparent, have been found in clefts around the Wannigletscher
(MinRec 56.3.296).
Aeschynite-(Y) from the Monte Cervandone area -
Image
At the type locality, the Urstad Feldspar Mine, Hidra, Flekkefjord, Norway,
aeschynite-(Y) occurs in a granite pegmatite.
Aeschynite-(Y) from Urstad - Image
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