Allanite

Allanite (also Lombaardit ( e)) is a collective term for the REE silicate minerals allanite - (Ce), allanite - (La), allanite - (Y) of Epidotgruppe with the chemical composition ( Casee ) ( Al2FeII ) ( Si3O11 ) O (OH). According to the predominant rare earth element, the corresponding Allanite carries the Appendix ( Ce) for Ce ( La) for lanthanum and (Y) for yttrium, with the former occurring in nature are most frequently. Alternatively, there is the notation (Ca, Y, Ln) ( Al2FeII ) ( Si3O11 ) O ( OH ), the Ln is the sum of all lanthanides symbol and not the single element of lanthanum (La) is. Were named after the minerals Thomas Allan, a Scottish mineralogist ( 1777-1833 ). The deprecated name orthite is no longer used today.

The brackets in the chemical formula elements take on different places in the crystal lattice together (A-, M -, T-, OH - place). By substitution of a number of other elements can be found in Allanite such as thorium, manganese, titanium, magnesium and trivalent iron, to name a few. Due to the virtually ever-present thorium content allanite is radioactive, optically isotropic, and often forms a radial system of cracks in the surrounding rock.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz included allanite - (Ce), allanite - (La) and allanite - (Y) to the mineral class of " silicates and Germanates " and then to the Department of " group silicates ( Sorosilikate ) "where she along with Dissakisit - (Ce), Dissakisit - (La), Dollaseit - (Ce), epidote, epidote - (Pb ) ( Hancockit ) Ferriallanit - (Ce), Gatelit - (Ce), Khristovit - (Ce), clinozoisite, clinozoisite - (Sr ) ( Niigatait ) Manganiandrosit - (Ce), Manganiandrosit - (La ) ( Androsit (LA ) ), Manganipiemontit - (Sr ) ( Tweddillit ) Mukhinit, piemontite, piemontite ( Sr) ( Strontiopiemontit ) Uedait - (Ce), Vanadoandrosit - (Ce), Västmanlandit - (Ce) and zoisite formed the independent Epidotgruppe.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns allanite - (Ce), allanite - (La) and allanite - (Y ) is also in the class of " silicates and Germanates " and there in the department of " group silicates ( Sorosilikate ) " a. This division, however, is further divided according to the structure of the silicate groups and the coordination of the cations involved, so that the mineral according to its construction in the subdivision of " group silicates with mixed SiO4 and Si2O7 groups; " Is to find where she became a member of the still existing " cations in octahedral and greater coordination. Epidotgruppe "with the system no 9.BG.05 form.

The mainly common in English-speaking classification of minerals according to Dana assigns allanite - (Ce), allanite - (La) and allanite - (Y) in the category of " silicates and Germanates " there, however, in the already fine subdivided Department of " group silicates: Insular, mixed, individual and larger tetrahedral groups. " Here they are together with epidote, epidote - (Pb), epidote - ( Sr), Gatelit - (Ce), clinozoisite, clinozoisite - ( Sr), Manganipiemontit - ( Sr), Mukhinit, piemontite, piemontite - ( Sr) and Uedait - (Ce ) in the " Epidotgruppe ( allanite - subgroup ) " 58.02.01c within the subdivision " group silicates: Insular, mixed, individual and larger groups with cations in tetrahedral and higher coordination; Single and double groups (n = 1,2) to find ".

Modifications and varieties

There is a whole series with allanite related minerals. Dissakisit and Dollaseit are Mg variants Ferriallanit contains Fe2 and Fe3 , Fe3 and Oxyallanit no OH group.

Education and Locations

Allanite is a common accessory constituent in many igneous rocks, particularly in granites, pegmatites, etc. Also in metamorphic rocks whose source rock containing corresponding proportions of rare earths, allanite is found. Moreover, allanite occurs as hydrothermal formation.

Crystal structure

Allanite - (Ce), allanite - (La) and allanite - (Y) crystallize in the monoclinic space group ( Raumgruppen-Nr. 11).

For allanite - (Ce), the lattice parameters were a = 8.93 Å; b = 5.76 Å; c = 10.15 Å and β = 114.8 ° and two formula units per unit cell determined.

For allanite - ( La), the lattice parameters were a = 8.94 Å; b = 5.726 Å; c = 114.7 Å, and 10:16 ° β = and 2 formula units per unit cell determined.

For allanite - (Y) the lattice parameters a = 8.98 Å were; b = 5.75 Å; c = 10:23 Å and β = 115 ° and two formula units per unit cell.

Use

Allanite constitutes a primary source of the metals of the rare earth group