|Karnassurt , Lowosero Tundra , Kola Peninsula , Russia|
|General and classification|
|chemical formula||(Na, H 3 O) 15 (Ca, Mn, REE) 6 Fe 3+ 2 Zr 3 Si 24 O 66 (O, OH) 6 Cl · nH 2 O|
(and possibly department)
|Silicates and Germanates|
System no. to Strunz
and to Dana
|9.CO.10 ( 8th edition : VIII / E.25)
|Crystal class ; symbol||ditrigonal-pyramidal 3 m|
|Room group (no.)||R 3 m (No. 160)|
|Lattice parameters||a = 14.167 Å ; c = 30.081 Å|
|Formula units||Z = 3|
|Density (g / cm 3 )||measured: 2.82; calculated: 2.63|
|Break ; Tenacity||clamshell; brittle|
|colour||brownish yellow to light brown|
|Line color||brownish white|
|transparency||transparent to translucent|
n ω = 1.612
n ε = 1.615
|Birefringence||δ = 0.003|
|Optical character||uniaxial positive (often also weakly biaxial)|
The mineral icranite is a very rare ring silicate from the eudialyte group with the chemical composition (Na, H 3 O) 15 (Ca, Mn, REE) 6 Fe 3+ 2 Zr 3 Si 24 O 66 (O, OH) 6 Cl nH 2 O. It crystallizes in the trigonal crystal system and has so far only been found in the form of transparent to translucent, granular aggregates up to about two to three centimeters in size from brownish-yellow to light brown in color with brownish-white streak color .
Etymology and history
The mineral was named after the Russian acronym IKRAN, which stands for the "Institut Kristallografii Rossiiskoi Akademii Nauk".
Was first discovered Ikranit with Raslakit on the mountain Karnassurt at Lovozero (Murmansk Oblast) on the Russian peninsula Kola . The minerals were analyzed and described by NV Chukanov, IV Pekov, AE Zadov, VV Korovushkin, IA Ekimenkova, RK Rastsvetaeva, who submitted their results together with the chosen name to the International Mineralogical Association (IMA) for examination of the mineral status. The application for the Ikranit received the receipt no. IMA 2000-010 and in the same year the mineral was recognized as independent. For the Raslakit ( IMA 2002-067 ) application and approval followed two years later. The discovery of new minerals was published in 2003 in the Zapiski Vserossijskogo mineralogičeskogo obŝestva .
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the ikranite belonged to the mineral class of "silicates and germanates" and there to the department of " ring silicates (cyclosilicates)", where together with Alluaivit , Carbokentbrooksit , Eudialyt , Feklichevit , Ferrokentbrooksit , Kentbrooksit , Khomyakovit , Manganokhomyakovit , Oneillit , Raslakit , Taseqit and Zirsilit- (Ce) formed a separate group.
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 assigns icranite to the class of "silicates and germanates" and there in the section of " ring silicates (cyclosilicates)". This division, however, is further subdivided according to the type of the ring structure, so that the mineral according to its structure in the subsection "[Si 9 O 27 ] 18 is found -Neuner-rings", where it together with Alluaivit, Andrianovit , Aqualith , Carbokentbrooksit, Dualith , Eudialyt, Feklichevit, Ferrokentbrooksit, Georgbarsanovit , Golyshevit , Johnsenit- (Ce) , Kentbrooksit, Khomyakovite, Labyrinthit , Manganokhomyakovite, Mogovidit , Oneillit, Rasqlakit, Tasevidit- the systemic group (Ce) -No. 9.CO.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the icranite to the class of "silicates and germanates", but there it is in the more finely divided division of "ring silicates: rings with other anions and insular silicate groups". Here he is also a member of the "eudialyte group" with the system no. 64.01.01 and the other members Eudialyt, Alluaivit, Kentbrooksit, Khomyakovit, Manganokhomyakovit, Oneillit, Ferrokentbrooksit, Feklichevit, Rastsvetaevit, Taseqit, Carbokentbrooksit, Zirsilit- (Ce), Labyrinthsanvit , Mogovidite, dualith and voroncovite can be found in the subsection “ Ring Silicates: Rings with Other Anions and Insular Silicate Groups with Mixed Ring Types ”.
The mineral 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 around 46 Bq / g (for comparison: natural potassium 31.2 Bq / g).
Education and Locations
Ikranite was found in two peralkaline pegmatites (magmatite with an excess of alkalis compared to aluminum) and occurred there in paragenesis with aegirin , lamprophyllite , lorenzenite , microcline , mrfvedsonite , murmanite and nepheline .
- NV Chukanov, IV Pekov, AE Zadov, VV Korovushkin, IA Ekimenkova, RK Rastsvetaeva: Ikranite, (Na, H 3 O) 15 (Ca, Mn, REE) 6 Fe 3+ 2 Zr 3 ( □, Zr) ( □ Si ) Si 24 O 66 (O, OH) 6 Cl · nH 2 O and raslakite Na 15 Ca 3 Fe 3 (Na, Zr) 3 Zr 3 (Si, Nb) (Si 25 O 73 ) (OH, H 2 O) 3 (Cl, OH): The new eudialyte-group minerals from Lovozero Massif, Kola Peninsula . In: Zapiski Vserossijskogo mineralogičeskogo obŝestva . tape 132 , no. 5 , ISSN 0869-6055 , p. 22-33 .
- RK Rastsvetaeva, NV Chukanov (2003): Ikranite: Composition and structure of a new mineral of the eudialyte group. In: Crystallography Reports. Volume 48, No. 5, pp. 717-720; translated from Kristallografiya. Volume 48, No. 5 (2003), pp. 775-778 doi : 10.1134 / 1.1612591