Usturit

from Wikipedia, the free encyclopedia
Usturit
General and classification
other names

Bitikleit- (ZrFe), IMA2009-053

chemical formula Ca 3 SbZrFe 3 O 12
Mineral class
(and possibly department) 		Oxides and hydroxides
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Ia 3 d (No. 230)Template: room group / 230
Lattice parameters a  = 12.669 (synthetic)
12.49 (natural)  Å
Formula units Z  = 8
Frequent crystal faces Rhombic dodecahedron {110}
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) calculated: 4.470
Cleavage Please complete!
colour light brown to yellow
Line color White
transparency Please complete!
shine Glass gloss
radioactivity very weak due to traces of uranium and thorium
magnetism antiferromagnetic below 11 ° K
Crystal optics
Refractive index n  = 1.9

The mineral usturite is a very rare oxide from the upper group of the garnet with the idealized composition Ca 3 SbZrFe 3 O 12 . It crystallizes in the cubic crystal system with the structure of garnet. The maximum 10 μm large crystals occur in aggregates with lakargiite and iron-rich kimzeyite .

So far (2017) Usturite 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

Sb garnets, including usturite (Ca 3 Sb 5+ Zr 4+ Fe 3+ 3 O 12 ), were synthesized as early as the 1970s and their magnetic properties were investigated.

In nature, Usturit was described by Irina O. Galuskina and colleagues under the name Bitikleit- (ZrFe) and was recognized as a new mineral in 2009 by the International Mineralogical Association (IMA). It was initially named after the historical fortress of Bitikle, not far from where it was found. When the garnet supergroup was reorganized in 2013, the mineral was renamed Usturit after the mountain Ustur near the type locality.

classification

The current classification of the International Mineralogical Association (IMA) counts the usturite to the garnet upper group, where together with Dzhuluit , Bitikleit and Elbrusit it forms the Bitikleit group with 9 positive charges on the tetrahedrally coordinated grid position.

The 9th edition of the Strunz'schen mineral systematics, valid since 2001 , does not list the Usturit. Although Usturit is not a silicate, it would, as katoite , due to its formation of mixed crystals with silicate shells into the garnet group with atomic number 9.AD.25 in the class of "silicates and Germanates" Division A (island silicates), subsection "D . Island silicates without further anions; Cations in octahedral [6] and usually greater coordination ”.

Crystal structure

Usturite crystallizes with cubic symmetry in the space group Ia 3 d (space group no. 230) with 8 formula units per unit cell . The synthetic end member has the lattice parameter a  = 12.669  Å , the natural mixed crystal from the type locality a  = 12.49 Å. Template: room group / 230

The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X-positions surrounded by 8 oxygen, antimony (Sb 5+ ) and zirconium (Zn 2+ ) the octahedral Y-position surrounded by 6 oxygen and the tetrahedral Z-position surrounded by 4 oxygen occupied with iron (Fe 3+ ).

Chemism

Usturit is the Zr analog of Dzhuluit and forms complex mixed crystals , especially with Kimzeyit and the hypothetical end link Usturit- (Al). The measured composition from the type locality is [X] (Ca 3.002 Th 0.001 ) [Y] (Sb 5+ 0.776 Zr 4+ 0.852 Sn 4+ 0.269 Ti 4+ 0.067 Mg 0.010 Nb 5+ 0.009 Hf 0.008 Cr 3+ 0.002 U 6 + 0.015 ) [Z] (Fe 3+ 1.548 Al 1.072 Si 0.167 Ti 4+ 0.130 Fe 2+ 0.080 V 5+ 0.002 ). This can be the following as mixed crystal, for. T. hypothetical termini can be expressed:

52% Usturit (Ca 3 Sb 5+ Zr 4+ Fe 3+ 3 O 12 ) with
25% Usturit- (Al) (Ca 3 Sb 5+ Zr 4+ Al 3+ 3 O 12 ) according to the exchange reaction

  • [Z] Fe 3+ = [Z] Al 3+ ,

11% Toturite- (TiAl) (Ca 3 Sn 4+ 3 Ti 4+ Al 3+ 2 O 12 ) according to the exchange reaction

  • [Y] (Sb 5+ Zr 4+ ) + [Z] (Fe 3+ 2 ) = [Y] (Sn 4+ Ti 4+ ) + [Z] (Ti 4+ Al 3+ 2 ),

5% morimotoite (Sn) Ca 3 Sn 4+ Fe 2+ Si 3 O 12 according to the exchange reaction

  • [Y] (Sb 5+ Zr 4+ ) + [Z] (Fe 3+ 3 ) = [Y] (Sn 4+ Fe 2+ ) + [Z] Si 4+ 3

4% Kimzeyit- (Ti) Ca 3 Zr 4+ 2 Ti 4+ Al 3+ 2 O 12 according to the exchange reaction

  • [Y] Sb 5+ + [Z] Fe 3+ 3 = [Y] Zr 4+ + [Z] (Ti 4+ Al 3+ 2 )

and 4% schorlomite (Al) Ca 3 Ti 4+ 2 Si 4+ Al 3+ 2 O 12 according to the exchange reaction

  • [Y] (Sb 5+ Zr 4+ ) + [Z] (Fe 3+ 3 ) = [Y] Ti 4+ 2 + [Z] (Si 4+ Al 3+ 2 ).

Education and Locations

Usturite has so far only been detected in 2 sites of 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 . It formed contact metamorphic in the sanidinite facies at temperatures above 800 ° C and low pressure in the cuspidin - hydrogrossular zone of calcium silicate carrons at the contact with the ignimbrite. Usturit occurs here in fine-grained aggregates of Lakargiit and iron-rich Kimzeyit, along with Cuspidin, Larnite , hydrogrossular, wadalite , Rondorfit , fluorite , Hydroxylellestadit , minerals of Ettringitgruppe , perovskite , Magnesioferrit , Afwillit , hillebrandite , Toberomit and Hydrocalumit .

See also

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o p q Irina O. Galuskina, Evgeny V. Galuskin, Thomas Armbruster, Biljana Lazic, Piotr Dzierżanowski, Viktor M. Gazeev, Krystian Prusik, Nikolai N. Pertsev, Antoni Winiarski, Aleksandr E. Zadov, Roman Wrzalik, and Anatoly G. Gurbanov: Bitikleite- (SnAl) and bitikleite- (ZrFe): New garnets from xenoliths of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northern Caucasus, Russia . In: American Mineralogist . tape 95 , no. 7 , 2010, p. 959–967 ( rruff.info [PDF; 1.4 MB ; accessed on July 8, 2017]).
  2. ↑ a b c d e AP Dodokin, S. Lyubutin, BV Mill, VP Peshkov: Mössbauer Effect In Antiferromagnetic Substances With Garnet Structures . In: Soviet Physics JETP . tape 36 , no. 3 , 1973, p. 526-531 ( jetp.ac.ru [PDF; 200 kB ; accessed on July 8, 2017]).
  3. ↑ a b List of localities for Usturite in the Mineralienatlas and Mindat
  4. ^ A b 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]).