Gadolinite
| Gadolinite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | (Y, Ce, Nd) 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2 |
|
Mineral class (and possibly department) |
Silicates and Germanates - island silicates |
|
System no. to Strunz and to Dana |
9.AJ.20 ( 8th edition : VIII / B.29) 54.02.01b |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / c (No. 14) |
| Lattice parameters | see crystal structure |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 6.5 to 7 |
| Density (g / cm 3 ) | 4 to 4.5 |
| Cleavage | no |
| Break ; Tenacity | shell-like, splintery; brittle |
| colour | greenish black to black, brown |
| Line color | gray-green |
| transparency | opaque; almost transparent in thin layers |
| shine | Greasy gloss, glass gloss |
| radioactivity | partly radioactive |
| Crystal optics | |
| Refractive indices |
n α = 1.770 n β = 1.790 n γ = 1.820 (gadolinite- (Y)) |
| Birefringence | δ = 0.050 (gadolinite- (Y)) |
| Optical character | biaxial positive |
| Axis angle | 2V = 85 ° (measured) |
Gadolinite is a short and collective name for the three minerals recognized by the International Mineralogical Association (IMA), gadolinite (Ce) , gadolinite (Nd) and gadolinite (Y) from the mineral class of " silicates and germanates ". The three minerals contain cerium , neodymium and yttrium as the named constituent elements of the so-called rare earth metals and form a complete mixed series , whose mixed crystals of different composition are generally referred to as gadolinite.
The idealized chemical composition of the theoretical end members is:
- Gadolinite (Ce) - Ce 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2
- Gadolinite (Nd) - Nd 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2
- Gadolinite- (Y) - Y 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2
The lattice sites of cerium are not only mostly occupied by yttrium, but often also by other rare earth metals. The chemical composition must therefore be specified more precisely with (Ce, SEE) 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2 or (Y, SEE) 2 Fe 2+ Be 2 O 2 (SiO 4 ) 2 .
Gadolinite crystallizes in the monoclinic crystal system and is mostly found as ingrown, imperfectly formed crystals with matt surfaces or in the form of coarse, brittle masses. Fresh fracture surfaces have a greasy glass gloss .
In general, gadolinite is opaque. Small crystals or thin layers can also be almost transparent. Its color varies from greenish black to black and brown. Thin layers are more grass green to olive green.
Etymology and history
The original name of gadolinite was ytterbit after it was first found in the Ytterby mine near Resarö in the Swedish municipality of Vaxholm .
Gadolinite (now Gadolinit- (Y) ) was first described in 1800 by Martin Heinrich Klaproth , who named the mineral in honor of Johan Gadolin (1760-1852), a Finnish chemist and mineralogist who discovered the element yttrium , among other things .
Gadolinit- (Ce) was first described in 1978 by Tom Victor Segalstad, Alf Olav Larsen from the type locality Buer near Skien in the Norwegian province of Telemark .
Gadolinit- (Nd) was first described in 2016 by Radek Škoda *, Jakub Plášil, Renata Čopjaková, Milan Novák, Erik Jonsson, Michaela Vašinová Galiová and Dan Holtstam.
classification
Already in the now outdated, but still common 8th edition of the mineral classification according to Strunz , the gadolinites belonged to the mineral class of "silicates and germanates" and there to the department of " island silicates with non-tetrahedral anions (Neso subsilicates)", where they were named after Datolith the "Datolith-Gadolinit-Gruppe" with the system no. VIII / B.29 and the other members Bakerite , Calcyberborosilit- (Y) , Hingganit- (Ce) , Hingganit- (Y) , Hingganit- (Yb) , Homilit and Minasgeraisit- (Y) .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies gadolinites in the category of "island silicates (nesosilicates)". This is, however, further subdivided according to the crystal structure, so that the mineral can be found according to its structure in the subsection " Island silicates with BO 3 triangles and / or B [4] , Be [4] tetrahedra, corner-dividing with SiO 4 ", where together with Bakerite, Calcybeborosilit- (Y), Datolite, Hingganit- (Ce), Hingganit- (Y), Hingganit- (Yb), Homilit, Melanocerit- (Ce) and Minasgeraisit- (Y) the "Datolite group" with the system no. 9.AJ.20 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the gadolinites to the class of "silicates and germanates" and there in the section of "island silicates: borosilicates and some beryllosilicates with (BO 3 )". Here it is together with bakerite, calciogadolinite, homilite and minasgeraisite- (Y) in the " datolith group (homilite series) " with the system no. 54.02.01b can be found in the subsection “ Island silicates: borosilicates and some beryllosilicates with B in [4] coordination”.
Crystal structure
All three minerals crystallize monoclinically in the space group P 2 1 / c (space group no.14) , but with slightly different lattice parameters :
- Gadolinite- (Y): a = 4.77 Å ; b = 7.56 Å; c = 10.00 Å and β = 90.3 ° and 2 formula units per unit cell .
- Gadolinite- (Ce): a = 4.82 Å; b = 7.58 Å; c = 10.01 Å and β = 90.5 ° and 2 formula units per unit cell.
- Gadolinite- (Nd): a = 4.8216 Å; b = 7.6985 Å; c = 10.1362 Å and β = 90.234 ° and 2 formula units per unit cell.
As an island silicate , the structure of the three minerals consists of isolated silicate tetrahedra , the oxygen corners of which are connected to one iron and one of the rare earth element ions. The beryllium ions are embedded in the gaps between the tetrahedra.
For a better representation of the crystal chemical structure, the formula can also be used with (Ce, SEE) 2 Fe 2+ Be 2 [4] O 2 [O | SiO 4 ] 2 or (Y, SEE) 2 Fe 2+ Be 2 [4 ] O 2 [O | SiO 4 ] 2 can be specified. This indicates that the Beryllium - cations by four oxygen - ion surrounded d. H. are fourfold coordinated . The inside the brackets from SiO 4 - tetrahedron partitioned oxygen indicates that this part is based only on the set before the bracket cations, while the oxygen of the SiO 4 is tetrahedra also bound to both the cations as silicon.
properties
Gadolinite often contains thorium (Th), a radioactive element from the group of actinides , as a further admixture . The storage of thorium not only ensures that the gadolinite becomes a radioactive α-emitter , but also destroys the crystal lattice over time. It “isotropizes” and becomes an amorphous metamict . Due to the radioactive radiation and the resulting destruction of the crystal system, the mineral eventually turns black and becomes opaque.
When heating z. B. in front of the soldering tube "glows" isotropized gadolinite with heat generation and becomes anisotropic . It is broken down by hydrochloric acid to form gelatinous layers.
Education and Locations
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Gadolinites are formed by contact metamorphosis in syenite - pegmatite veins between basalt and monzonite or in alkaline granite pegmatites . As Begleitminerale occur among other Aegirin , albite , Allanit , apatite , Apophyllit , biotite , calcite , Chevkinit , fluorite , fergusonite , Helvin , loparite , magnetite , microcline , molybdenite , Prochlor , Pyrophanit , quartz , titanite , Yttrialit , zircon .
In Germany, gadolinite (Ce) has so far only been found in a gabbro quarry in the Radau valley near Bad Harzburg in Lower Saxony.
In Austria, too, gadolinite (Ce) has so far only been known from one site, an emerald deposit in the Leckbachgraben on the Nasenkopf in the Habach Valley in the Salzburg High Tauern . In addition, gadolinite (Y) was found in two outcrops near Böckstein in the Gastein Valley (Salzburg) and in the Ober schrammacherscharte in the Tyrolean Zillertal .
Gadolinite- (Nd) is only known from its type locality , the Malmkärra mine in the municipality of Norberg in the Swedish province of Västmanland County.
In Switzerland, gadolinite (Y) is also known from several sites in the Val Nalps in the municipality of Tujetsch in the canton of Graubünden, from the Val Bedretto and near the Carona district in the canton of Ticino and from several sites in the Binn valley in the canton of Valais.
Other locations for gadolinite (Ce) and gadolinite (Y) are in Argentina, Australia, China, Finland, France, Italy, Japan, Canada, Kazakhstan, Malawi, Mongolia, Norway, Pakistan, Poland, Portugal, Russia , Sweden, Switzerland, Spain, South Africa, South Korea, Tajikistan, Hungary, the United Kingdom (Great Britain) and the United States (USA).
use
As an ore, gadolinite is of little importance despite its high rare earth content between 38 and 50% by weight due to its rarity. However, it is occasionally offered in a polished form for collectors.
See also
literature
- Martin Heinrich Klaproth: Chemical investigation of the gadolinite . In: Contributions to the chemical knowledge of mineral bodies . tape 3 , 1802, pp. 52–79 ( rruff.info [PDF; 523 kB ; accessed on October 27, 2017]).
- Tom Victor Segalstad, Alf Olav Larsen: Gadolinite- (Ce) from Skien, southern Oslo region, Norway . In: American Mineralogist . tape 63 , 1978, pp. 188–195 ( rruff.info [PDF; 806 kB ; accessed on October 27, 2017]).
- Gadolinite- (Ce) . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 71 kB ]).
- Gadolinite- (Y) . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 75 kB ]).
Web links
- Mineral Atlas : Gadolinit- (Ce) , Gadolinit- (Nd) and Gadolinit- (Y) (Wiki)
- mindat.org: Gadolinite- (Ce) , Gadolinite- (Nd) and Gadolinite- (Y)
- RRUFF Database-of-Raman-spectroscopy: Gadolinite- (Y) and Gadolinite- (Ce)
Individual evidence
- ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 563 .
- ↑ a b c Mindat - Gadolinite- (Ce) and Mindat - Gadolinite- (Y)
- ↑ a b c IMA / CNMNC List of Mineral Names; September 2017 (PDF 1.67 MB)
- ^ A b Paul Ramdohr , Hugo Strunz : Klockmanns textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 685 to 386 .
- ↑ Tom Victor Segalstad, Alf Olav Larsen: Gadolinite- (Ce) from Skien, southern Oslo region, Norway . In: American Mineralogist . tape 63 , 1978, pp. 188–195 ( rruff.info [PDF; 806 kB ; accessed on October 27, 2017]).
- ↑ a b U. Hålenius, F. Hatert, M. Pasero, SJ Mills: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC). Newsletter 32. New minerals and nomenclature modifications approved in 2016 . In: Mineralogical Magazine . tape 80 , no. 5 , 2016, p. 915–922 ( main.jp [PDF; 97 kB ; accessed on October 27, 2017]).
- ^ Gadolinite- (Ce) , in: Handbook of Mineralogy
- ^ Gadolinite- (Y) , in: Handbook of Mineralogy
- ↑ a b c List of sites for gadolinite (Ce) , gadolinite (Nd) and gadolinite (Y) in the Mineralienatlas as well as for gadolinite (Ce) , gadolinite (Nd) and gadolinite (Y) in Mindat
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 226 .