Fergusonite

Fergusonite, more α - fergusonite is a common mineral from the mineral class of sulfates, etc., more precisely the molybdates, tungstates and niobates. There are a total of three minerals with that name known to the Fergusonite - Y which consists solely of yttrium niobate Fergusonite -C, wherein addition of cerium and lanthanum are not contained and not recognized by the IMA Fergusonite Nd, additionally including neodymium and titanium. However, these two are much rarer than fergusonite -Y.

Fergusonite Y crystallizes in the tetragonal crystal system with the chemical composition and forms YNbO4 prismatic to acicular dipyramidal crystals up to 20 cm size. Also massive grains are known.

Etymology and history

Fergusonite -Y was first found in 1826 by Wilhelm Ritter von Haidinger in the type locality, the island Qeqertaussaq near Atammik Greenland. It was named after the Scottish physicist Robert Ferguson. After initially assumed that Fergusonite is a mineral that was later recognized that this is a mineral series in which different minerals can be distinguished with different composition.

Classification

In the classification by Strunz Fergusonite is classified differently depending on the edition. In the 8th edition of the Fergusonite minerals together with Formanit ( Y) and a subset of the Raspit oxides having a ratio of metal to oxygen of 1:2. In the 9th edition, it is one of the molybdates and tungstates without additional anions or water, a subset of the sulfates and forms Formanit - (Y), Powellit, scheelite, and Stolzit Wulfenite the scheelite group.

In the classification by the Dana Fergusonite and Formanit - (Y) form a distinct group within the oxides of Nb, Ta and Ti and the ratio formula A BO4.

Modifications and varieties

A variety of Ferguson Y Risörit having the composition (Y, Er) (Nb, Ti, Ta) (O, OH) 4, and up to five weight percent of contained titanium ( IV) oxide. Dimorphic to the fergusonite - minerals are the corresponding β - fergusonite minerals.

Education and Locations

Fergusonite formed in lanthanide -containing pegmatite rocks. It is associated with monazite, gadolinite Thalenit, euxenite, allanite, zircon, biotite and magnetite. The mineral is widespread, but occurs only in low concentrations.

Finds are known in addition to the type locality, among others, from the Norwegian provinces Østfold and Aust- Agder, the Eifel region of Rhineland -Palatinate, Ytterby in Sweden, Madagascar, Piedmont in Italy, the Valais ( Switzerland ) and the U.S. states of Colorado and Texas.

Crystal structure

Fergusonite -Y crystallizes in the tetragonal crystal system, space group I41 / a with lattice parameters a = 5.15 Å and c = 10.89 Å and four formula units per unit cell.