Fergusonite is a mineral comprising a
complex oxide of various rare-earth elements. The general chemical formula of fergusonite is (Y,REE)NbO
4, where REE = rare-earth elements in solid solution with
Y. Yttrium is usually dominant (the mineral in this case being referred to as fergusonite-(Y)), but sometimes
Ce or
Nd may be the major rare-earth component (in fergusonite-(Ce) and fergusonite-(Nd), respectively). The other
rare-earth elements are present in smaller amounts, and
tantalum sometimes substitutes for some of the
niobium
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
. There are
Fergusonite-beta-(Nd), Fergusonite-beta-(Y), Fergusonite-beta-(Ce) forms too, but they are classified as 4.DG.10 in the
Nickel–Strunz system. The mineral has
tetragonal crystal symmetry and the same structure as
scheelite (calcium tungstate, CaWO
4), but can be
metamict (amorphous) due to radiation damage from its small content of
thorium. It is found as needle-like or prismatic crystals in
pegmatite
A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...
. It was named after British politician and mineral collector
Robert Ferguson of Raith (1767–1840).
Robert Ferguson of Raith
University of Edinburgh.
See also
* List of minerals
* List of minerals named after people
References
Lanthanide minerals
Niobium minerals
Oxide minerals
Tetragonal minerals
Minerals in space group 88
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