Bayan Obo

fergusonite-(Ce) CeNbO4.0.3H2O
fergusonite-(Ce)-β CeNbO4
fergusonite-(Nd)-β NdNbO4
fergusonite-(Y) YNbO4
fergusonite-(Y)-β YNbO4
Multiple oxides containing the rare earth elements niobium Nb, cerium Ce, neodymium Nd and yttrium Y, usually metamict.

Specific gravity: Ce 5.48; Ce-β 5.34; Nd-β 6.45; Y 4.2 to 5.7; Y-β 5.65
Hardness: 5½ to 6½ (All)
Ce reddish brown
Ce-β pale rose
Nd-β pale brown
Y brown, yellow-brown, greenish grey
Ce dark red to black
Ce-β red, reddish brown
Nd-β red, brownish red, yellowish brown
Y black to brownish grey, grey, yellow, brown
Y-β yellow
Solubility: Fergusonite-(Ce)-β is insoluble in acids (AM 62.397).

Placer deposits
Metamorphic environments


At Bayan Obo, Inner Mongolia, China, fergusonite-(Ce) occurs in magnesium-rich skarn of the outer granite contact zone of a carbonatite-derived dolomitic marble (HOM). At the type locality, the Chernigovskiy Massif, Zaporizhia Oblast, Ukraine, fergusonite-(Ce) occurs in a carbonatite associated with magnetite, phlogopite, graphite, chlorite, quartz, pyrite, columbite, allanite, bastnäsite, parisite, apatite, aeschynite, fersmite, monazite, calcite and dolomite (HOM, Dana, AM 74.946).


At the type locality, the Bayan Obo deposit, Baotou League, Inner Mongolia, China, fergusonite-(Ce)-β occurs in magnesian skarn around carbonatite-derived dolomitic marble, associated with diopside, phlogopite and apatite (Dana, AM 60.485).


At the type locality, the West Mine, Bayan Obo deposit, Baotou League, Inner Mongolia, China, fergusonite-(Nd)-β occurs in a niobium-rare earth deposit in riebeckitised dolomite associated with riebeckite, ferroan dolomite, biotite, magnetite, monazite, bastnäsite, aeschynite-(Nd), ilmenite, pyrite and fergusonite-(Ce) (Dana, AM 69.406-407).


Fergusonite-(Y) is a typical mineral of rare-earth-bearing granite pegmatites, and it also occurs in placers. Associated minerals include monazite, gadolinite, thalénite, euxenite, allanite, zircon, biotite and magnetite (HOM).

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 (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).


At Mount Cervandone in the Western Alps of Italy, an arsenic-rich variety of fergusonite-(Y)-β occurs in cavities within pegmatite dikes, associated with quartz, biotite, potassium feldspar, and synchysite-(Ce). The fergusonite crystallised under amphibolite facies conditions (AM 95.487-494).

At the type locality, Asht-Sai, Shaidan Massif, Kuraminskii Range, Sughd, Tajikistan, fergusonite-(Y)-β occurs in microcline granite rocks (Dana, Webmin).

Common impurities: U,Th

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