Menzerite- (Y)

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Menzerite- (Y)
General and classification
other names

IMA 2009-050

chemical formula Y 3+ 2 Ca 2+ Mg 2+ 2 Si 3 O 12
Mineral class
(and possibly department) 		Silicates and Germanates
System no. according to Strunz 9.AD.25
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  = 11.9947 (natural mixed crystal)  Å
Formula units Z  = 8
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) natural mixed crystal: 4.31 (calculated)
Cleavage not observed
colour red-brown
Line color Please complete!
transparency Please complete!
shine Please complete!
Crystal optics
Refractive index n  = 1.844 (natural mixed crystal)
Birefringence isotropic

The mineral menzerite- (Y) is an extremely rare island silicate from the garnet group and has the idealized chemical composition Y 3+ 2 Ca 2+ Mg 2+ 2 Si 3 O 12 . It crystallizes in the cubic crystal system with the structure of garnet.

Menzerite- (Y) occurs in the form of red-brown cores of almandine inclusions in potassium feldspar , which are rarely larger than 70 µm.

Menzerite- (Y) is formed when regional metamorphosis begins in andesitic to basaltic magmas . The type locality and the only known site to date (2018) is a granulite from Bonnet Island in Georgian Bay in the Parry Sound District , Ontario , Canada .

Etymology and history

The first reports of yttrium in garnet date back to 1868. Dana's System of Mineralogy from 1892 lists analyzes by Websky that show 2.64% by weight yttrium oxide in manganese-rich garnet.

The structure of garnet was not yet known. Max von Laue , Walther Friedrich and Paul Knipping laid the basis for their determination in 1912 with the discovery of X-ray diffraction , for which Laue received the Nobel Prize in Physics in 1914 . Eleven years later, in 1925, Georg Menzer determined the crystal structure of Granat and later became a research assistant at Max von Laue himself.

Van der Lingen introduced the names Emildin for yttrium-containing spessatin and Erinadin for yttrium-containing spessartine-pyrope-uvarowite mixed crystals in his investigation of grenades from South Africa in 1928 . Further evidence of trace contents of yttrium and other rare earth metals in garnets followed, including Goldschmidt and Peters (1931), Björlykke (1937), Iimori (1938) with 2.45% by weight rare earth oxide and Sahama and Vähätalo (1939) until Jaffe found 1951 that yttrium is a common component of Spessartine-rich garnets made from pegmatites . Jaffe explained the incorporation of yttrium via the coupled exchange Mn 2+ + Si 4+ = Y 3+ + Al 3+ .

Yoder & Keith from the Geophysical Laboratory of the Carnegie Institution for Science provided experimental confirmation of this mechanism of yttrium incorporation in garnet in the same year. They were able to synthesize the complete mixture of Spessartine to Yttrium-Aluminum-Garnet (YAG, Yttrogranat) (Y 3+ 3 Al 3+ 2 Al 3+ 3 O 12 ).

Natural garnets that incorporate yttrium via this mechanism rarely contain more than 1–2% by weight of yttrium oxide. It took almost 60 years until menzerite- (Y), an yttrium-rich garnet with around 17% by weight of Y 2 O 3 , was described. These high yttrium contents are achieved with a different mechanism of incorporation of yttrium, in which the charge balance is not achieved by replacing Si 4+ with Al 3+ , but by replacing Al 3+ with Mg 2+ . This new garnet with the final link composition Y 3+ 2 Ca 2+ Mg 2+ 2 Si 3 O 12 was named after the crystallographer and former professor at the Ludwig Maximilians University of Munich Georg Menzer, in recognition of his research on the structure of the garnet.

classification

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

The outdated, but still in use 8th edition of the mineral classification according to Strunz does not yet list the menzerite (Y). He would, together with almandine, Andradite, Calderit, Goldmanit, Grossular, Henritermierit , Hibschite , Holtstamit , Hydrougrandit , katoite , Knorringit, Morimotoit, majorite, pyrope, Schorlomit , Spessartin, Uwarowit and wadalite in the "Garnet" with the system no. VIII / A.08 belong within the department of " Island Silicates (Nesosilicates)".

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 , does not yet know the menzerite (Y) either. It would become a "garnet group" with the system no. 9.AD.25 belong within the department of "Island Silicates (Nesosilicates)". This is further subdivided according to the possible presence of further anions and the coordination of the cations involved , so that the mineral is 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 systematics of minerals according to Dana , which is mainly used in the English-speaking world , does not yet list the menzerite (Y) either.

Chemism

Menzerite- (Y) with the idealized composition [X] (Y 3+ 2 Ca 2+ ) [Y] Mg 2+ 2 [Z] Si 3 O 12 is the yttrium - magnesium analog of Grossular.

For the most yttrium-rich menzerite (Y) from the type locality, the following composition is given:

  • [X] (Ca 1.37 Y 0.83 Gd 0.01 Dy 0.05 Ho 0.02 Er 0.07 Tm 0.01 Yb 0.06 Lu 0.02 Fe 2+ 0.49 Mn 2+ 0 , 07 ) [Y] (Mg 2+ 0.55 Fe 2+ 0.42 Fe 3+ 0.58 Al 3+ 0.35 V 3+ 0.01 Sc 3+ 0.01 Ti 4+ 0.08 ) [Z] (Si 2.82 Al 3+ 0.18 ) O 12 ,

where [X], [Y] and [Z] indicate the positions in the garnet structure.

This natural menzerite (Y) can be described as a complex mixed crystal with grossular, andradite and an Fe 2+ analog of menzerite, corresponding to the exchange reactions

  • [X] Y 3+ + [Y] Mg 2+ = [X] Ca 2+ + [Y] Al 3+ ( grossular )
  • [X] Y 3+ + [Y] Mg 2+ = [X] Ca 2+ + [Y] Fe 3+ ( andradite )
  • [Y] Mg 2+ = [Y] Fe 2+ (Ferro-Menzerite- (Y))

and small proportions of Hutcheonite and Spessartine, accordingly

  • [X] Y 3+ + [Y] Mg 2+ + [Z] Si 4+ = [X] Ca 2+ + [Y] Ti 4+ + [Z] Al 3+ ( Hutcheonite )
  • [X] Y 3+ + [Y] Mg 2+ = [X] Mn 2+ + [Y] Al 3+ ( Spessartine ).

The exchange vector for Y incorporation described by Yaffe and Yodder & Keith in 1951

  • [X] Ca 2+ + [Z] Si 4+ = [X] Y 3+ + [Z] Al 3+

does not play a special role for menzerite- (Y).

The exchange reaction assumed for a Y-rich garnet from Japan

  • 2 [X] Ca 2+ = [X] Y 3+ + [X] Na +

was confirmed for gneiss garnets containing sodium and yttrium in China. Up to 2% by weight of rare earth oxide was incorporated into these grenades via this mechanism. This exchange reaction is not active with menzerite.

Theoretical calculations of the energy balance for the Y incorporation via various exchange reactions confirm this picture. Menzerite substitution and the coupled Y-Na incorporation are energetically favorable. The charge balance via vacancies in the X position, Al in the silicon position (YAG) or lithium (Li) in the octahedral aluminum position proved to be energetically less favorable .

Crystal structure

Menzerite- (Y) 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  = 11.9947  Å . Template: room group / 230

The structure is that of garnet . Yttrium (Y 3+ ) and calcium (Ca 2+ ) occupy the dodecahedral X-position surrounded by 8 oxygen ions, magnesium (Mg 2+ ) the octahedral Y-position surrounded by 6 oxygen ions and the tetrahedral Z-position surrounded by 4 oxygen ions Occupied exclusively with silicon (Si 4+ ).

Education and Locations

Yttrium is a common component of Spessartine-rich garnets made from rare earth pegmatites . However, the yttrium content of this garnet does not exceed a few% by weight.

The type locality and the so far (2018) only known site of menzerite- (Y) is a rockic granulite from Bonnet Island in Georgian Bay in the Parry Sound District , Ontario , Canada . Menzerite- (Y) is found in the core of yttrium-containing almandines and occurs together with potassium feldspar , allanite- (Ce) , ilmenite and fluoroapatite . Other minerals of the surrounding rock with which menzerite does not come into direct contact are oligoclase , wortite , ferrosilite , augite , clinoamphibol , biotite , magnetite and, as an accessory, zircon , monazite - (Ce), xenotime - (Y), pyrite , chalcopyrite , sphalerite , Hercynite and Mg-Fe carbonate.

Menzerite- (Y) formed with increasing metamorphosis at 550 - 780 ° C and 5 - 8.5 kbar in thermodynamic equilibrium with oligoclase, ferrosilite, quartz, clinopyroxene and iron oxides. The sources of the rare earth metals were primarily xenotime and subordinate to zircon. When melting began, menzerite (Y) was broken down again and eventually overgrown by almandine.

See also

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o Edward S. Grew, Jeffrey H. Marsh, Martin G. Yates, B. Lazic, T. Armbruster, Martin Locock, SW Bell, MD Dyar, HJ Bernhardt , O. Medenbach: Menzerite- (Y), a new species, {(Y, REE) (Ca, Fe2 +) 2} [(Mg, Fe2 +) (Fe3 +, Al)] (Si3) O12, from a felsic granulite, Parry Sound, Ontario, and a new garnet end-member, {Y2Ca} [Mg2] (Si3) O12. In: The Canadian Mineralogist . tape 48 , 2010, p. 1171–1193 ( unibe.ch [PDF; 5.3 MB ; accessed on March 4, 2018]).
  2. ↑ a b List of localities for menzerite (Y) in the Mineralienatlas and in Mindat
  3. ^ A b c d e Howard W. Jaffe: The role of yttrium and other minor elements in the garnet group. In: The American Mineralogist . tape 36 , 1951, pp. 133–155 ( minsocam.org [PDF; 1.5 MB ; accessed on March 6, 2018]).
  4. ↑ a b HS Yoder & ML Keith: Complete substitution of aluminum for silicon: the system 3MnO • Al2O3 • 3SiO2 - 3Y2O3 • 5Al2O3. In: The American Mineralogist . tape 36 , 1951, pp. 519-533 ( minsocam.org [PDF; 892 kB ; accessed on March 6, 2018]).
  5. ^ 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]).
  6. ↑ Masaki Enami, Bolin Cong, Takeyoshi Yoshida, Iwao Kawabe: A mechanism for Na incorporation in garnet: An example from garnet in orthogneiss from the Su-Lu terrane, eastern China . In: The American Mineralogist . tape 80 , 1995, pp. 475-482 ( minsocam.org [PDF; 675 kB ; accessed on March 12, 2018]).
  7. ^ William D. Carlson, Julian D. Gale, Kate Wright: Incorporation of Y and REEs in aluminosilicate garnet: Energetics from atomistic simulation . In: The American Mineralogist . tape 99 , 2014, pp. 1022-1034 ( minsocam.org [PDF; 999 kB ; accessed on March 10, 2018]).
  8. ↑ Jeffrey H. Marsh, Edward S. Grew, Christopher C. Gerbi, Martin G. Yates and Nicholas G. Culshaw: The Petrogenesis Of The Garnet Menzerite- (Y) In Granulite Facies Rocks Of The Parry Sound Domain, Grenville Province, Ontario . In: The Canadian Mineralogist . tape 50 , 2012, p. 73-99 , doi : 10.3749 / canmin.50.1.73 .