Dualith
| Dualith | |
|---|---|
| General and classification | |
| other names |
IMA 2005-019 |
| chemical formula | Na 30 (Ca, Na, Ce, Sr) 12 (Na, Mn, Fe, Ti) 6 MnTi 3 Zr 3 [(OH, H 2 O, Cl) 9 | (Si 3 O 9 ) 4 | (Si 9 O 27 ) 4 · 3 SiO] |
|
Mineral class (and possibly department) |
Please complete |
|
System no. to Strunz and to Dana |
9.CO.10 ( 8th edition : VIII / E.25) 64.01.01.21 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-pyramidal; 3 m |
| Room group (no.) | R 3 m (No. 160) |
| Lattice parameters | a = 14.153 (9) Å ; c = 60.72 (5) Å |
| Formula units | Z = 3 |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 2.84 (3); calculated: 2.814 |
| Cleavage | Please complete |
| Break ; Tenacity | clamshell; brittle |
| colour | yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| radioactivity | slightly |
| Crystal optics | |
| Refractive indices |
n ω = 1.610 (1) n ε = 1.613 (1) |
| Optical character | uniaxial positive |
The mineral Dualith is a very rare ring silicate from the eudialyte group with the chemical formula Na 30 (Ca, Na, Ce, Sr) 12 (Na, Mn, Fe, Ti) 6 MnTi 3 Zr 3 [(OH, H 2 O, Cl) 9 | (Si 3 O 9 ) 4 | (Si 9 O 27 ) 4 · 3 SiO]. The elements indicated in the round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral.
Dualith crystallizes in the trigonal crystal system and has so far only been found in the form of xenomorphic grains 0.3 to 0.5 millimeters in diameter, yellow in color with white streak color .
Etymology and history
The mineral was first discovered in 2005 on Mount Alluaiw on the Russian Kola peninsula and described by AP Khomyakov, GN Nechelyustov and RK Rastsvetaeva, who derived it from the Latin word dualis ("containing two.") Because of its close and simultaneous relationship to zirconosilicates and titanosilicates “) Called a dualith.
The type material of the Dualith is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences in Moscow.
classification
Since the Dualith was only recognized as an independent mineral in 2005, it is not listed in the Strunz mineral system (8th edition), which has been outdated since 2001 . Only the "Lapis mineral directory" published in 2008, which is still based on the classic system of Karl Hugo Strunz out of consideration for private collectors and institutional collections , lists the mineral under system no. VIII / E.25-95 .
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the dualith to the class of “silicates and germanates” and there to the “ ring silicates (cyclosilicates)” section. However, this section is further subdivided according to the structure of the rings, so that the mineral can be found according to its structure in the sub-section "[Si 9 O 27 ] 18 - Neuner rings", where it can be found together with Alluaivite , Aqualith , Carbokentbrooksite , Eudialyte , Feklichevit , Ferrokentbrooksit , Georgbarsanovit , Golyshevit , Ikranit , Andrianovit , Johnsenit- (Ce) , Kentbrooksit , Khomyakovit , Labyrinthit , Manganokhomyakovit , Mogovidit , Oneillit , Raslakit , Rastsvetaevit , Taseqit and Zirsilit- (Ce) , the "Eudialytgruppe" with the system No. 9.CO.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the dualith to the class of "silicates and germanates", but there in the department of "ring silicates: rings with other anions and insular silicate groups". Here he is also in the "eudialyte group" with the system no. 64.01.01 and the other members Eudialyt, Alluaivit, Kentbrooksit, Khomyakovite, Manganokhomyakovit, Oneillit, Ferrokentbrooksit, Ikranit, Feklichevit, Rastsvetaevit, Taseqit, Carbokentbrooksit, Zirsilit- (Ce), Labyrinthit- (Ce), Labyrinthit-, Cekovit , Golyshevit, Mogovidit and Voronkovite can be found in the subsection “ Ring Silicates: Rings with Other Anions and Insular Silicate Groups with Mixed Ring Types ”.
Crystal structure
Dualith crystallizes trigonal in the space group R 3 m (space group no. 160) with the lattice parameters a = 14.153 (9) Å and c = 60.72 (5) Å; as well as 3 formula units per unit cell .
properties
Dualith is classified as slightly radioactive due to small admixtures of radioactive isotopes of various rare earth metals (REE) and zirconium and has a specific activity of about 69 Bq / g (for comparison: natural potassium 31.2 Bq / g).
Education and Locations
Dualith is so far (as of 2012) only known from the type locality Alluaiw in Russia. There it was found in the peralkaline pegmatoid of the Lowosero pluton together with K-Na feldspar , nepheline , sodalite , cancrinite , aegirine , alkali amphiboles , eudialyte , loocerite , lomonosovite , vuonnemite , lamprophyllite , sphalerite and villiaumite .
See also
literature
- AP Khomyakov, GN Nechelyustov, RK Rastsvetaeva: Dualite, Na30 (Ca, Na, Ce, Sr) 12 (Na, Mn, Fe, Ti) 6Zr3Ti3MnSi51O144 (OH, H2O, Cl) 9, a new zircono-titanosilicate with a modular eudialyte -like structure from the Lovozero alkaline Pluton, Kola Peninsula, Russia , in: Geology of Ore Deposits , Volume 50/7 (2008), pp. 574-582 doi : 10.1134 / S1075701508070088
Web links
- Mineral Atlas: Dualith (Wiki)
Individual evidence
- ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ a b Webmineral - Dualite
- ↑ a b Mindat - Dualite