Fergusonite is a mineral comprising a

complex oxide A complex oxide is a chemical compound that contains oxygen and at least two other elements (or oxygen and just one other element that's in at least two oxidation states). Complex oxide materials are notable for their wide range of magnetic and el ...

of various rare-earth elements. The general chemical formula of fergusonite is (Y,REE)NbO₄, 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 element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

s are present in smaller amounts, and

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

sometimes substitutes for some of the niobium. 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 In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...

crystal symmetry and the same structure as

scheelite Scheelite is a calcium tungstate mineral with the chemical formula Ca W O4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist K. Scheele (1742-1786). Well-formed crystals are sought by collectors ...

(calcium tungstate, CaWO₄), but can be

metamict Metamictisation (sometimes called metamictization or metamiction) is a natural process resulting in the gradual and ultimately complete destruction of a mineral's crystal structure, leaving the mineral amorphous. The affected material is therefore ...

(amorphous) due to radiation damage from its small content of

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...

. It is found as needle-like or prismatic crystals in pegmatite. It was named after British politician and mineral collector

Robert Ferguson of Raith Robert Ferguson (8 September 17693 December 1840) of Raith, was at various times a Whig Member of Parliament for Fifeshire, Haddingtonshire and Kirkcaldy Burghs, and at the time of his death he was Lord Lieutenant of the county of Fif ...

(1767–1840).Robert Ferguson of Raith
University of Edinburgh.

References

Lanthanide minerals Niobium minerals Oxide minerals Tetragonal minerals Minerals in space group 88 {{oxide-mineral-stub

See also

References