Mariinsit

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Mariinsit
General and classification
other names

IMA 2011-057

chemical formula BeCr 2 O 4
Mineral class
(and possibly department) 		Oxides and hydroxides
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnma (No. 62)Template: room group / 62
Lattice parameters a  = 9.727 (3)  Å ; b  = 5.619 (1) Å; c  = 4.499 (1) Å
Formula units Z  = 4
Physical Properties
Mohs hardness 8.5 (VHN 150 = 1725 kg / mm 2 )
Density (g / cm 3 ) 4.25
Cleavage no
Break ; Tenacity shell-like
colour dark green
Line color light green
transparency translucent, transparent in thin layers
shine strong glass luster
Crystal optics
Refractive indices n α  = 2.05 (1)
n β  = 2.09 (3)
n γ  = 2.15 (1)
Birefringence δ = not defined
Optical character biaxial positive
Axis angle 2V = 80 ± (10) ° (calculated 80.5 °)
Pleochroism visible: X = emerald green; Y = yellow green; Z = greenish yellow

Mariinskit is a very rare mineral from the mineral class of "oxides and hydroxides". It crystallizes in the orthorhombic crystal system with the sum formula BeCr 2 O 4 , is the chroman analogue of chrysoberyl (BeAl 2 O 4 ) and the beryllium analogue of chromite (FeCr 2 O 4 ). Chemically, Mariinskit can also be viewed as beryllium chromate (III) or beryllium chromite.

Mariinskit could so far only be found in the form of irregular grains from 0.01 to 0.3 millimeters in size from dark green to emerald green in color with light green streak color . In some cases pseudo-hexagonal crystal forms were also found , which resemble those of chrysoberyl twins . The mineral is mostly translucent and only transparent in thin layers. The crystal surfaces have a strong, glass-like sheen .

Etymology and history

Mariinskit was first discovered in 2011 in the “Mariinskoye” emerald deposit near Malysheva in the Russian Oblast of Sverdlovsk and described in 2012 by LA Pautov, MP Popov, Yu. V. Erokhin, VV Khiller and V. Yu. Karpenko, who named the mineral after its type locality .

classification

Since the mineral was only discovered in 2011, the last update of the mineral classification according to Strunz (9th edition) , which is also used by the International Mineralogical Association (IMA), but took place in 2009, no official classification into a specific mineral group is known.

Since the Mariinskit is a very closely related mineral to the Chrysoberyl , Mariinskit will probably also be assigned to the department of oxides with the molar ratio metal: oxygen = 3: 4 and comparable ones and there to the sub-department “With small and medium-sized cations ”.

Crystal structure

Mariinskit crystallizes orthorhombically in the space group Pnma (space group no. 62) with the lattice parameters a  = 9.727 (3)  Å ; b  = 5,619 (1) Å; c  = 4.499 (1) Å and 4 formula units per unit cell . Template: room group / 62

Education and Locations

Mariinskite formed in chromitite , an igneous ultramafic rock that consists mainly of the mineral chromite . As accessory mineral occurred fluorphlogopite , chromium-containing muscovite , eskolaite and tourmaline on.

Its type locality , the “Mariinskoye” emerald deposit in Russia, is also the only known site for Mariinskit in the world.

See also

literature

  • LA Pautov, MP Popov, Yu. V. Erokhin, VV Khiller, V. Yu. Karpenko: Mariinskite, BeCr 2 O 4 , a New Mineral, Chromium Analog of Chrysoberyl In: Geology of Ore Deposits. Volume 55, No. 8 (2013), ISSN  1075-7015 , pp. 648-662 doi : 10.1134 / S1075701513080096 (Originally published in Russian by Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2012, No. 6, pp. 43-62)
  • Dmitriy Belakovskiy, G. Diego Gatta, Fernando Cámara: New Mineral Names. In: American Mineralogist. Volume 99, 2014, pp. 242–247 ( PDF 4.23 MB ; Mariinskite pp. 5–6)

Web links

Individual evidence

  1. ↑ a b c NA Yamnova, SM Aksenov, LA Pautov, MP Popov, Yu. V. Erokhin; Specific features of cation distribution in the crystal structure of mariinskite BeCr2O4 (Derivative of olivine-type structure); Crystallography reports; 59 (2014) pp. 30–35.
  2. ↑ compare Chromite in AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , pp. 1450-1451.
  3. ↑ IMA / CNMNC List of Mineral Names 2009 (PDF 1.8 MB)
  4. ↑ Find location list for Mariinskit at the Mineralienatlas and at Mindat