Eringait

from Wikipedia, the free encyclopedia
Eringait
General and classification
chemical formula Ca 3 Sc 3+ 2 Si 3 O 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)Template: room group / 230
Lattice parameters a  = synthetic: 12.250
natural: 12.19  Å
Formula units Z  = 8
Physical Properties
Mohs hardness not determined
Density (g / cm 3 ) calculated: 3.654
Cleavage no
Break ; Tenacity uneven
colour natural: light brown to yellow,
synthetic: colorless
Line color creamy white
transparency Please complete!
shine Glass gloss
Crystal optics
Refractive index n  = not determined
Birefringence isotropic

The mineral eringaite is a rare silicate from the upper group of the garnet with the idealized chemical composition Ca 3 Sc 3+ 2 Si 3 O 12 . It crystallizes in the cubic crystal system with the structure of garnet.

In its type locality , a rodingitartigen skarn from the river Vilyuy River in the Republic Sacha (Yakutia), Russia , Eringait occurs in the form of a few microns large, light brown to yellow zones and stains in Schorlomit - and Kerimasitreichen grenades. In addition, it has so far (as of 2017) only been detected in a few meteorites, where it occurs as an inclusion in diopside . It is believed that eringaite was one of the earliest silicate condensates from the presolar nebula .

Etymology and history

In the course of systematic investigations of the chemically very variable garnet group, scandium-containing garnets and eringaite were artificially produced as early as the 1970s.

The first natural scandium-containing garnets were found in rodingite-like skarns on the banks of the Vilyui River in Yakutia, Russia, in 2005. The scandium garnet eringaite was also described in the same rock 5 years later. It was named after the river Eringa, which flows into the Wiljui opposite the site.

Since then, eringaite has only been found as a submicroscopic inclusion in some meteorites.

classification

The structural classification of the International Mineralogical Association (IMA) is one of the Eringait to Garnet supergroup, where he together with Menzerit- (Y) , pyrope , Grossular , Spessartin , almandine , Goldmanit , Momoiit , Knorringit , Uwarowit , Andradite , Calderit , Rubinit , Majorite and morimotoite form the garnet group with 12 positive charges on the tetrahedrally coordinated lattice position.

The 8th edition of the mineral classification according to Strunz , which is now outdated, but still in use in some cases, does not list the eringait. Only in Stefan Weiß's "Lapis Mineral Directory", which, out of consideration for private collectors and institutional collections, is still based on the classic system of Karl Hugo Strunz , was the mineral given system no. VIII / A.08-145 and would thus along with almandine, Andradite, Calderit, Goldmanit, Grossular, Henritermierit , Hibschite , Holtstamit , Hydrougrandit , katoite , Kimzeyit , Knorringit, majorite, Morimotoit, pyrope, Schorlomit, Spessartin, Uwarowit, wadalite and Yamatoit (discredited because it is identical to Momoiit ) to the "garnet group" with the system no. VIII / A.08 within the department of the " island silicates include (nesosilicates)".

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), does not yet list the eringait either. Here, however, it would also be classified under the category of "island silicates (nesosilicates)". This is further subdivided here according to the possible presence of further anions as well as the coordination of the cations involved , so that the mineral is classified according to its composition and structure in the subdivision of “island silicates without additional anions; Would cations published in octahedral [6] and to find usually greater coordination, "where it along with almandine, Andradite, Calderit, Goldmanit, Henritermierit , Holtstamit , katoite , Kimzeyit , Knorringit, majorite, Morimotoit, pyrope, Schorlomit , Spessartin and Uwarowit to the "garnet group" with the system no. 9.AD.25 would be counted. The garnet compounds blythite, hibschite, hydroandradite and skiagite, which are no longer regarded as minerals, were also included in this group. Wadalite , at that time still grouped with the grenades, proved to be structurally different and is now assigned to a separate group with chloromayenite and fluoromayenite . The garnets irinarassite , hutcheonite , kerimasite , toturite and menzerite- (Y) described after 2001 would have been sorted into the garnet group.

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , would also place the Eringait in the class of "silicates and Germanates" and there in the department of "island silicate minerals ". Here it would be together with andradite, goldmanite, uwarovite and yamatoite in the "garnet group (Ugrandite series)" with the system no. 51.04.03b within the subsection “ Island silicates: SiO4 groups only with cations in [6] and> [6] coordination ”.

Chemism

Eringaite is the scandium (Sc) analog of Grossular and forms complex mixed crystals , especially with kimzeyite, schorlomite and andradite. The measured composition from the type locality is

  • [X] (Ca 2.98 Y 0.01 Mg 0.01 ) [Y] (Sc 3+ 0.82 Ti 4+ 0.44 Fe 3+ 0.30 Zr 4+ 0.21 Mg 2+ 0, 10 Al 3+ 0.09 Cr 3+ 0.08 Fe 2+ 0.05 V 3+ 0.01 ) [Z] (Si 2.48 Al 0.30 Fe 3+ 0.22 ) O 30 .

The Ti and Zr contents in the Y position, together with the Fe 3+ and Al contents in the Z position, result in mixed crystal formation with shorlomitic garnets ( [X] Ca 3 [Y] (Zr, Ti) 4 + 2 [Z] ((Fe, Al) 3+ 2 Si) O 12 ) back, corresponding to the exchange reaction

  • [Y] Sc 3+ + [Z] Si 3+ = [Y] (Ti, Zr) 4+ + [Z] (Al, Fe) 3+

The Fe 3+ contents in the Y position can be attributed to the admixture of andradite [X] Ca 3 [Y] Fe 3+ 2 [Z] Si 4+ 3 O 12 in accordance with the exchange reaction

  • [Y] Sc 3+ = [Y] Fe 3+

to be led back.

The meteoritic Eringaite contain similar amounts of scandium (Sc), no Fe 3+ but significantly more yttrium (Y) and titanium (Ti 3+ !):

  • [X] (Ca 2.31 Mg 0.56 Y 0.09 Fe 2+ 0.05 ) [Y] (Sc 3+ 0.82 Y 0.48 Ti 3+ 0.32 Ti 4+ 0.25 Zr 4+ 0.10 V 3+ 0.03 Cr 3+ 0.01 ) [Z] (Si 2.47 Al 0.44 Ti 4+ 0.09 ) O 30

Crystal structure

Eringaite 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  = 12.250  Å , the natural mixed crystal from the type locality a  = 12.19 Å. Template: room group / 230

The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, scandium (Sc 3+ ) the octahedral Y position surrounded by 6 oxygen ions and the tetrahedral Z position surrounded by 4 oxygen ions is completely covered with silicon (Si 4+ ) occupied.

Education and Locations

Eringaite forms in contact metamorphic skarns or as a condensate from the presolar nebula at low pressure and high temperatures .

Skarn

The type locality of Eringait is a Rodingitartiger skarn from the river Vilyuy River in the Republic of Sakha (Yakutia), Russia . Accompanying minerals are grossular , andradite and perovskite .

Meteorites

In CV3 chondrites , eringaite is found in calcium-aluminum-rich inclusions (CAIs). In the Vigarano meteorite it occurs as inclusion in davisite and Sc-rich diopside , together with tazheranite , hexaferrum and MgAl spinel .

In the Allende meteorite, eringaite also occurs as an inclusion in Sc-rich diopside, together with spinel and Y-containing perovskite.

See also

Web links

Individual evidence

  1. ^ A b c d e f g h i j k l m n IO Galuskina, EV Galuskin, B. Lazic, T. Armbruster, P. Dzierzanovski, K. Prusik and R. Wrzalik: Eringaite, Ca3Sc2 (SiO4) 3, a new mineral of the garnet group . In: Mineralogical Magazine . tape 74 , no. 2 , 2010, p. 365-373 ( researchgate.net [PDF; 955 kB ; accessed on September 9, 2017]).
  2. ↑ a b c d BV Mill, EL Belokoneva, MA Simonov, NV Belov: Refined crystal structures of the scandium garnets Ca3Sc2Si3O12, Ca3Sc2Ge3O12, and Cd3Sc2Ge3O12 . In: Journal of Structural Chemistry . tape 18 , no. 2 , 1977, p. 321–323 ( springer.com [PDF; 169 kB ; accessed on September 9, 2017]).
  3. ↑ a b Simona Quartieri, Roberta Oberti, Massimo Boiocchi, Maria Chiara Dalconi, Federico Boscherini, Olga Safonova, and Alan B. Woodland: Site preference and local geometry of Sc in garnets: Part II. The crystal-chemistry of octahedral Sc in the andradite-Ca3Sc2Si3O12 join . In: American Mineralogist . tape 91 , 2006, p. 1240–1248 ( rruff.info [PDF; 443 kB ; accessed on September 9, 2017]).
  4. ↑ Find location list for Eringait at the Mineralienatlas and at Mindat
  5. ↑ a b c d e Chi Ma: DISCOVERY OF METEORITIC ERINGAITE, Ca3 (Sc, Y, Ti) 2Si3O12, THE FIRST SOLAR GARNET? In: 75th Annual Meteoritical Society Meeting (2012) . 2012 ( usra.edu [PDF; 70 kB ; accessed on September 9, 2017]).
  6. ↑ a b c d AN Krot, K. Nagashima, C. Ma, GJ Wasserburg, U. Hawa: FORSTERITE-BEARING TYPE B CAI WITH A RELICT ERINGAITE-BEARING ULTRA-REFRACTORY CAI . In: 78th Annual Meteoritical Society Meeting (2015) . 2015 ( usra.edu [PDF; 96 kB ; accessed on September 9, 2017]).
  7. ↑ Irina O. Galuskina, Evgeny V. Galuskin, Piotr Dzierzanovski, Thomas. Armbruster and Marcin Kozanecki: A natural scandian garnet . In: American Mineralogist . tape 90 , 2005, pp. 1688–1692 ( amazonaws.com [PDF; 924 kB ; accessed on September 9, 2017]).
  8. ^ 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 ( main.jp [PDF; 2,3 MB ; accessed on July 8, 2017]).