Irinarassit
| Irinarassit | |
|---|---|
| General and classification | |
| other names |
IMA 2010-073 |
| chemical formula | Ca 3 Sn 2 Al 2 SiO 12 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | Ia 3 d (No. 230) |
| Lattice parameters | a = 12.50 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | not determined |
| Density (g / cm 3 ) | calculated: ~ 4.30 |
| Cleavage | no |
| Break ; Tenacity | uneven |
| colour | yellow to pale brown |
| Line color | pale yellowish gray |
| transparency | translucent |
| shine | not defined |
| radioactivity | sometimes weakly radioactive due to uranium incorporation |
| Crystal optics | |
| Refractive index | n = ~ 1.9 (calculated) |
| Birefringence | isotropic |
The mineral irinarassite is a very rare silicate from the upper group of garnets with the idealized chemical composition Ca 3 Sn 2 Al 2 SiO 12 . It crystallizes in the cubic crystal system with the structure of garnet and is found in small areas or small patches in Kimzeyit - Kerimasit -rich grenades or as few microns large crystals in transformation products of zircon .
So far (2017) Irinarassite has only been detected in its type locality , a calcium silicate xenolite from an ignimbrite from Mount Lakargi, Chegem Caldera in the North Caucasian Republic of Kabardino-Balkaria in Russia .
Etymology and history
Artificially produced tin- rich garnets with up to 26% by weight SnO 2 occur together with cassiterite in slag from tin smelting .
Natural tin-containing garnets are very rare. In a few tin-bearing skarns, andradites with up to 5.8% by weight SnO 2 were found, and the Sn garnets Bitikleit , Dzhuluit and Toturite were found in the sanidinite-facial lime-silicate foreign rock inclusions of the Ignimbrite of the Chegem Caldera . In this xenolite , Galuskina's group discovered an Sn-Al-silicate garnet. They named the new mineral after Irina Teodorovna Rass, an employee at the Institute for Geology of Ore Deposits , Petrography, Mineralogy and Geochemistry (IGEM) of the Russian Academy of Sciences in Moscow . She is a well-known specialist in the petrology and geochemistry of alkali-rich, ultra-basic carbonatite complexes , lamproites and kimberlites .
classification
The current classification of the International Mineralogical Association (IMA) counts the irinarassite to the garnet upper group, where together with kimzeyite , hutcheonite , schorlomite , kerimasite and toturite it forms the schorlomite group with 10 positive charges on the tetrahedral coordinated lattice position.
The outdated, but still in use 8th edition of the mineral classification according to Strunz does not yet list the Irinarassit. He would, together with almandine Andradite , Calderit , Goldmanit , Grossular , Henritermierit , Hibschite , Holtstamit , Hydrougrandit , katoite , Knorringit , majorite , Morimotoit , pyrope , Schorlomit , Spessartin , Uwarowit , wadalite and Yamatoit (discredited because identical to Momoiit ) for " Garnet group "with the system no. VIII / A.08 in the section of " Island Silicates (Nesosilicates)".
Even the 9th edition of Strunz's mineral systematics, which has been in effect since 2001 , does not yet know the Irinarassit. Here he would also use the "garnet group" with the system no. 9.AD.25 within the division of "Island Silicates (Nesosilicates)". However, this is further subdivided according to the possible presence of further anions and the coordination of the cations involved , so that the mineral can be classified according to its composition in the subsection “Island silicates without additional anions; Cations in octahedral [6] and usually greater coordination ”would be found. The grenade described after 2001 Hutcheonit , Kerimasit , Toturit , Menzerit- (Y) and Eringait would have been sorted into the garnet group.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , would classify the Irinarassit in the department of "island silicate minerals ". Here it would be together with kimzeyite, schorlomite and morimotoite in the "garnet group (schorlomite-kimzeyite series)" with the system no. 51.04.03c within the subsection “ Island silicates: SiO 4 groups only with cations in [6] and> [6] coordination ”.
Chemism
Irinarassite is the Sn-Al analogue of schorlomite and forms complex mixed crystals , especially with kimzeyite, kerimasite and schorlomite. The measured composition from the type locality is
- [X] (Ca 2.965 Fe 2+ 0.035 ) [Y] (Sn 4+ 1.016 Zr 4+ 0.410 Ti 4+ 0.262 Sb 5+ 0.237 Fe 2+ 0.035 U 6+ 0.017 Sc 3+ 0.014 Hf 4+ 0.006 Nb 5+ 0.004 ) [Z] (Al 1.386 Fe 3+ 0.804 Si 0.446 Ti 4+ 0.262 ),
where [X], [Y] and [Z] indicate the positions in the garnet structure.
The compositions of the mixed crystals can be expressed with various combinations of terminal links. Irinarassite and kimzeyite and hutcheonite are largely miscible according to the exchange reactions
- [Y] Sn 4+ = [Y] Zr 4+ (Kimzeyit)
- [Y] Sn 4+ = [Y] Ti 4+ (Hutcheonite)
as well as the Fe 3+ minerals of the schorlomite group schorlomite, kerimasite and toturite according to the exchange reaction
- [Z] Al 3+ = [Z] Fe 3+
In addition, Irinarassite contains about 10% of the octahedral coordinated Y-position Sb 5+ , corresponding to a mixed crystal formation with ferrite garnets of the bitite-conductive group with the exchange reaction
- [Y] Sn 4+ + [Z] Si 4+ = [Y] Sb 5+ + [Z] (Al, Fe) 3+ (Bitikleit / Dzhuluit).
The Ti contents in the Z position can be added as an admixture of a Ti analogue of Irinarassite, which has so far only been known synthetically, [X] Ca 3 [Y] Sn 4+ 2 [Z] (Al 2 Ti 4+ ) O 12 according to the exchange reaction
- [Z] Si 4+ = [Z] Ti 4+
to be discribed.
Crystal structure
Irinarassite crystallizes with cubic symmetry in the space group Ia 3 d (space group no. 230) with 8 formula units per unit cell . The natural mixed crystal from the type locality has the lattice parameter a = 12.50 Å .
The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, tin (Sn 4+ ) the octahedral Y position surrounded by 6 oxygen ions and the tetrahedral Z position surrounded by 4 oxygen ions is aluminum (Al 3+ ) and silicon (Si 4+ ) occupied.
Education and Locations
Irinarassite is formed at low pressure and high temperatures around 800–1000 ° C in contact-metamorphic, Sn-bearing skarns as a conversion product of zircon , grown on kerimasite.
The type locality of irinarassite is a carbonate-rich xenolite in the ignimbrite of Mount Lakargi, Chegem Caldera in the North Caucasian Republic of Kabardino-Balkaria in Russia . Here, irinarassite occurs in the larnite - cuspidin zone of xenolite number 7 at the contact with ignimbrite. Begleitminerale addition Kerimasit-Kimzeyit mixed crystals, Lakargiit and Tazheranit also Larnite, baddeleyite , Baghdadit and perovskite .
See also
Web links
- Mineral Atlas: Irinarassite (Wiki)
- Mindat - Irinarassite (English)
Individual evidence
- ↑ a b c d e f g h i j k l m n IO Galuskina, EV Galuskin, K. Prusik, VM Gazeev, NN Pertsev and P. Dzierżanowski: Irinarassite Ca3Sn2SiAl2O12 - new garnet from the Upper Chegem Caldera, Northern Caucasus, Kabardino -Balkaria, Russia . In: Mineralogical Magazine . tape 77 , no. 6 , August 2013, p. 2857-2866 ( psu.edu [PDF; 1.4 MB ; accessed on September 25, 2017]).
- ↑ a b Mindat - Irinarassite (English)
- ↑ Find location list for Irinarassite in the Mineralienatlas and in Mindat
- ^ BCM Butler: Tin-rich garnet, pyroxene, and spinel from a slag . In: Mineralogical Magazine . tape 42 , December 1978, p. 487–492 ( rruff.info [PDF; 464 kB ; accessed on September 25, 2017]).
- ^ Edward S. Grew, Andrew J. Locock, Stuart J. Mills, Irina O. Galuskina, Evgeny V. Galuskin and Ulf Hålenius: IMA Report - Nomenclature of the garnet supergroup . In: American Mineralogist . tape 98 , 2013, p. 785–811 ( rruff.info [PDF; 1.1 MB ; accessed on April 28, 2020]).
- ↑ Hisanori Yamane, Tetsuya Kawano: Preparation, crystal structure and photoluminescence of garnet-type calcium tin titanium aluminates . In: Journal of Solid State Chemistry . tape 184 , no. 5 , 2011, p. 965-970 , doi : 10.1016 / j.jssc.2011.02.016 .