Formula: YNbO4
Multiple oxide containing the rare earth elements niobium Nb and yttrium Y, usually metamict, tetragonal
paramorph of fergusonite-(Y)-β,
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 Murchison, Ontario, Canada, fergusonite-(Y) occurs with euxenite (Dana).
The type locality for fergusonite-(Y) is Kangeq, Sermersoq Island, Kujalleq, Greenland, Denmark.
At Hundholman, Norway, fergusonite-(Y) occurs with allanite,
fluorite variety yttrofluorite, xenotime and
gadolinite (Dana).
At Iveland, Norway, fergusonite-(Y) occurs in pegmatites with gadolinite and
thalénite-(Y) (Dana).
At the Blum mine, Ilmenskie mountains, Russia, fergusonite-(Y) occurs with samarskite
and rutile variety ilmenorutile (Dana).
At Ytterby, Sweden, fergusonite-(Y) occurs in a pegmatite with xenotime,
zircon variety 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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