Formula: YNbO4
Multiple oxide containing the rare earth elements niobium Nb and yttrium Y, usually metamict, tetragonal
paramorph of clinofergusonite-(Y),
which is monoclinic, fergusonite group
Specific gravity: 4.2 to 5.7
Hardness: 5½ to 6½
Streak: brown, yellow-brown, greenish grey
Colour: black to brownish grey, grey, yellow, brown
Common impurities: U,Th
Environments
Fergusonite-(Y) is a typical mineral of rare-earth-bearing granite pegmatites,
and it also occurs in placers. Associated minerals include monazite,
gadolinite, thalénite-(Y),
euxenite, allanite,
zircon, biotite and
magnetite (HOM).
Localities
At the J.G. Gole Quarry, Murchison Township, Nipissing District, Ontario, Canada, fergusonite-(Y) occurs with
euxenite
(Dana).
The type locality for fergusonite-(Y) is Kangeq, Sermersoq Island, Kujalleq, Greenland, Denmark.
At Iveland, Agder, Norway, fergusonite-(Y) occurs in
pegmatites with
gadolinite and
thalénite-(Y)
(Dana).
At Hundholmen, Narvik, Nordland, Norway, fergusonite-(Y) occurs
allanite, yttrofluorite,
xenotime and
gadolinite
(Dana).
At Buer, Bjørkedalen, Porsgrunn, Vestfold og Telemark, Norway, fergusonite-(Y) has been found in sparse
amounts on the dump from a water tunnel. Gadolinite-(Ce) was
discovered in the same dump, although not from the same
pegmatite. The
fergusonite-(Y) occurs as millimetre-sized tabular crystals in small vugs together with
bavenite and helvine, and is
obviously a late-crystallised mineral
(JWW p156).
At the Blum mine, Ilmenskie mountains, Russia, fergusonite-(Y) occurs with
samarskite
and ilmenorutile
(Dana).
At Ytterby, Resarö, Vaxholm, Stockholm County, Sweden, fergusonite-(Y) occurs in a
pegmatite with
xenotime,
cyrtolite and biotite
(Dana).
At Spruce Pine, Mitchell county, North Carolina, USA, fergusonite-(Y) occurs in
pegmatites with
allanite
(Dana).
At Barringer Hill, Llano county, Texas, USA, fergusonite-(Y) occurs with
gadolinite and
other rare earth minerals
(Dana).
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