Fergusonite
| Fergusonite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | YNbO 4 |
|
Mineral class (and possibly department) |
Sulphates - molybdates, tungstates, and niobates |
|
System no. to Strunz and to Dana |
7.GA.05 ( 8th edition : IV / D.24) 8.1.1.1 |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | 4 / m |
| Space group | I 4 1 / a |
| Lattice parameters | a = 5.15 Å ; c = 10.89 Å Please complete the source as an individual reference |
| Formula units | Z = 4 Please complete the source as an individual reference |
| Physical Properties | |
| Mohs hardness | 5.5 to 6.5 |
| Density (g / cm 3 ) | 5.6 to 5.8 |
| Cleavage | weak |
| Break ; Tenacity | subchonchoidal |
| colour | gray, yellow, brown |
| Line color | brown |
| transparency | opaque |
| shine | dull |
| Crystal optics | |
| Refractive index | n = 2.05 to 2.19 |
Fergusonite , more precisely α-fergusonite, is a widespread mineral from the mineral class of sulfates etc., more precisely of molybdates , tungstates and niobates . A total of three minerals with this name are known, fergusonite-Y , which consists solely of yttrium and niobate, fergusonite-Ce , which also contains cerium and lanthanum , and fergusonite-Nd , which is not recognized by the IMA , which also contains Contains neodymium and titanium . However, these two are significantly rarer than fergusonite-Y.
Fergusonite-Y crystallizes in the tetragonal crystal system with the chemical composition YNbO 4 and forms prismatic to needle-shaped dipyramidal crystals up to 20 cm in size. Solid grains are also known.
Etymology and history
Fergusonite-Y was first found in 1826 by Wilhelm Ritter von Haidinger in the type locality , the Qeqertaasaq peninsula near Atammik on Greenland . It was named after the Scottish physicist Robert Ferguson . After initially assuming that fergusonite is just a mineral, it was later recognized that this is a mineral series in which different minerals with different compositions can be distinguished.
classification
In the Strunz system , fergusonite is classified differently depending on the edition. In the 8th edition , the fergusonite minerals together with formanite (Y) and raspite form a subgroup of oxides with a metal to oxygen ratio of 1: 2. In the 9th edition it is one of the molybdates and tungstates without additional anions or water, a subgroup of sulfates and forms the scheelite group with formanite (Y), powellite , scheelite , stolzite and wulfenite .
In the Dana system , the fergusonites and formanite (Y) form a separate group within the oxides with Nb, Ta and Ti and the ratio formula A BO 4 .
Modifications and varieties
A variety of Ferguson-Y is risörite with the composition (Y, Er) (Nb, Ti, Ta) (O, OH) 4 and titanium (IV) oxide contained up to five percent by mass . The corresponding β-fergusonite minerals are dimorphic to the fergusonite minerals .
Education and Locations
Fergusonite forms in lanthanide- containing pegmatite rocks. It is associated with monazite , gadolinite , thalenite , euxenite , allanite , zirconium , biotite and magnetite . The mineral is widespread, but only occurs in low concentrations.
In addition to the type locality, finds are known from the Norwegian provinces of Østfold and Aust-Agder , the Eifel in Rhineland-Palatinate , Ytterby in Sweden , Madagascar , Piedmont in Italy , Valais ( Switzerland ) and the US states of Colorado and Texas .
Crystal structure
Fergusonite-Y crystallizes in the tetragonal crystal system in the space group I4 1 / a with the lattice parameters a = 5.15 Å and c = 10.89 Å as well as four formula units per unit cell .
See also
Individual evidence
literature
- Fergusonit-Y in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( pdf ).
