Thortveitite

Thortveitite is a rarely occurring mineral from the mineral group of silicates and Germanates. It crystallizes in the monoclinic crystal system with the chemical composition (Sc, Y) 2Si2O7 and forms prismatic, up to 35 cm large crystals of gray-green to black in color. Sometimes you will also colorless crystals or bleue.

Etymology and history

The mineral was found in 1911 by the Norwegian mineralogist Olaus Thortveit in the type locality Ljosland in the Norwegian province of Aust- Agder and described by J. Schetelig. It is named after Thortveit.

Classification

In the classification by Strunz thortveitite is counted among the group of silicates. After the 8th edition forms together with Gittinsit, Keiviit - (Y) Keiviit ( Yb), Kristiansenit, Percleveit ( Ce), Rowlandit ( Y) and Yttrialith (Y ) group. In the 9th edition it forms with Gittinsit, Keiviit - (Y), Keiviit - (Yb ) and Yttrialit - (Y ) is a subgroup of the group of silicates with Si2O7 groups and without non- tetrahedral anions. The cations are in octahedral and / or other coordination.

In the classification by Dana it forms with calcium oxide, Manganosit, Monteponit, periclase, wustite and Hongquiit the Periklasgruppe, a subgroup of the simple oxides with a cation charge of 2 .

Modifications and varieties

Scandium can be thortveitite replaced by various other elements. These include, in particular, yttrium, lanthanides such as ytterbium and lutetium, as well as up to 10% of thorium, zirconium, hafnium, calcium, or manganese can be included. Manganese is responsible for the blue coloration of the Thortveritits that can be found in Italy in the granite of Baveno.

Education and Locations

Thortveitite forms in granitic pegmatite dykes. Probably the complexation of scandium 2 in the emergence plays a role with fluorine as [ ScF ]. The mineral varies by locality associated with euxenite, biotite, oligoclase, microcline and quartz; Monazite, fergusonite, Ilmenorutil, beryl, muscovite, and magnetite or Kobeit, Perrierit, Tourmaline, euxenite, monazite, zircon, allanite, magnetite and ilmenite.

There are (as of February 2010) 48 localities for thortveitite known. In addition to the type locality and further discoveries in the Norwegian provinces of Aust- Agder, Finnmark and Telemark, one finds the mineral inter alia Obersulzbachtal in Austria, Paraíba in Brazil, Marathon in Canada, Linwu in China, Pello in Finland, Luzenac in France, Thiemendorf in Germany, several places in Italy, Kyoto Prefecture in Japan, Befanamo in Madagascar, Świdnica in Poland, the Urals and the Kola Peninsula in Russia, several places in Sweden and Ravalli County and Odgensburg in the United States.

Crystal structure

Thortveitite crystallizes in the monoclinic crystal system, space group C2 / m with lattice parameters a = 6.65 Å; b = 8.616 Å; c = 4.686 Å and β = 102.2 ° and one formula unit per unit cell. The Si2O7 anions are in the form of corner-sharing double tetrahedra. These are kantenverküpft with ScO6 octahedra and come in layers in the crystal structure before.

Use

Thortveitite is an important scandium mineral.