Kimzeyit

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Kimzeyit
General and classification
chemical formula Ca 3 Zr 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)Template: room group / 230
Lattice parameters a  = 12.46 (natural)
12.456 (synthetic)  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 7th
Density (g / cm 3 ) measured: 3.94; calculated: 4.03
Cleavage Please complete!
colour dark brown, synthetic end link is colorless
Line color light brown
transparency Please complete!
shine Glass gloss
Crystal optics
Refractive index n  = 1.94 (measured); 1.946 (calculated)
Birefringence isotropic, rarely low birefringence due to lattice stresses

The mineral kimzeyite is a rare silicate from the upper group of the garnet with the idealized chemical composition Ca 3 Zr 2 Al 2 SiO 12 . It crystallizes in the cubic crystal system with the structure of garnet. The often inclusive , dark brown crystals are rarely larger than 1 mm and show a combination of rhombic dodecahedron and deltoidic tetrahedron surfaces .

Apart from its type locality , a carbonatite from the Kimzey calcite quarry (Calcite Hill) in the Magnet Cove Complex, Hot Spring County , Arkansas , USA , Kimzeyite has so far (2017) only been described at around 14 other sites, including some carbonatites, basic to ultra-basic igneous rocks and skarns .

Etymology and history

Kimzeyit was discovered in 1953 by Joe W. Kimzey from Malvern, Arkansas. The high Zr content of these garnets was not determined until 5 years later, which in 1958 led to the first description of kimzeyite as a new mineral with the composition Ca 3 (Zr, Ti) 2 (Al, Fe 3+ , Si) 3 O 12 . In 1967 it was recognized as a new mineral by the International Mineralogical Association (IMA). When the garnet supergroup was reorganized, the formula for pure kimzeyite was changed to Ca 3 Zr 2 Al 2 SiO 12 .

It was named in honor of the Kimzey family, who mineralogically accompanied the economic development of the Magnet Cove complex from the early 1870s and supplied numerous collections worldwide with minerals from this deposit.

In the course of systematic investigations into the mixing behavior of grenades of the schorlomite group, kerimasite, then still known as kinzeyite, was synthesized in 1967 by Ito and Frondel and kinzeyite in 1993 by Yamakawa and his colleagues.

Current work is investigating kimzeyite, kerimasite, elbrusite and other garnets containing hafnium and zirconium with regard to their suitability for the final disposal of high-level radioactive waste from nuclear power plants.

classification

The current classification of the International Mineralogical Association (IMA) counts the kimzeyite to the garnet upper group, where together with irinarassite , hutcheonite , schorlomite , kerimasite and toturite it forms the schorlomite group with 10 positive charges on the tetrahedral coordinated lattice position.

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Kimzeyit belonged to the department of the "island silicates (nesosilicates)" where he collaborated with almandine Andradite , Calderit , Goldmanit , Grossular , Henritermierit , Hibschite , Holtstamit , Hydrougrandit , katoite , Knorringit , majorite , Morimotoit , Pyrop , Schorlomit , Spessartin , Uwarowit , wadalite and Yamatoit (discredited because identical to Momoiit ) the "garnet group" with the system number. VIII / A.08 .

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies kimzeyite in the category 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 “can be found, where it is found together with almandine, andradite, calderite, goldmanite, grossular, henritermierite, holtstamite, katoite, knorringite, majorite, morimotoite, pyrope, schorlomite, spessartine and uwarowite the "garnet group" with the system no. 9.AD.25 forms. 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 , menzerite (Y) and eringaite described after 2001 would have been classified in the garnet group.

The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , also classifies Kimzeyit in the category of "island silicate minerals ". Here it is together with 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

Kimzeyite is the Zr-Al analog of schorlomite and forms complex mixed crystals mainly with kerimasite , schorlomite and andradite . Natural kinzeyite usually shows very complex zoning and contains Al and Fe 3+ in approximately equal amounts. Kimezeyite and Kerimasite can only be distinguished with precise chemical analyzes and consideration of the zoning. The measured composition from the type locality is

  • [X] Ca 3.11 [Y] (Zr 4+ 1.42 Ti 3+ 0.40 Mg 2+ 0.07 Fe 2+ 0.07 Nb 5+ 0.05 ) [Z] (Al 1.26 Fe 3+ 0.98 Si 0.94 )

or.

  • [X] (Ca 2.94 Mg 0.05 ) [Y] (Zr 4+ 1.72 Ti 4+ 0.26 Nb 5+ 0.09 ) [Z] (Al 0.87 Fe 3+ 1.09 Si 0.94 )

or

  • [X] Ca 2.99 [Y] (Zr 4+ 1.48 Ti 4+ 0.37 Fe 3+ 0.15 ) [Z] (Al 0.87 Fe 3+ 0.98 Si 1.15 ).

The first wet-chemically determined composition by Milton et al. is possibly adulterated by inclusions of other minerals, the other two contain more Fe in the Z position than Al and, strictly speaking, represent the Fe analogue kerimasite according to the exchange reaction

  • [Z] Al 3+ = [Z] Fe 3+

At temperatures above 700 ° C there is a complete Mischbarbeit of synthetic Kimzeyit and Kerimasit. At lower temperatures, the miscibility of these components is limited and two coexisting grenades form, a Kinzeitreich and a Kerimasitreich. This segregation was also observed in natural kimzeyite from the type locality.

The complex compositions of the mixed crystals can be expressed with various combinations of end links. The Ti contents in the Y position can be added as an admixture of Hutcheonite [X] Ca 3 [Y] Ti 4+ 2 [Z] (Al 2 Si) O 12 according to the exchange reaction

  • [Y] Zr 4+ = [Y] Ti 4+

or Schorlomite [X] Ca 3 [Y] Ti 4+ 2 [Z] (Fe 3+ 2 Si) O 12 according to the exchange reaction

  • [Y] Zr 4+ + [Z] Al 3+ = [Y] Ti 4+ + [Z] Fe 3+

to be discribed. Furthermore, Kimzeyite forms mixed crystals with andradite [X] Ca 3 [Y] Fe 3+ 2 [Z] Si 3 O 12 according to the exchange reaction

  • [Y] Zr 4+ + [Z] Al 3+ = [Y] Fe 3+ + [Z] Si 4+

and with morimotoite-type garnets [X] Ca 3 [Y] (Zr, Ti) 4+ [Y] (Fe, Mg) 2+ [Z] Si 3 O 12 according to the exchange reaction

  • [Y] Zr 4+ + 2 [Z] Al 3+ = [Y] (Fe, Mg) 2+ + 2 [Z] Si 4+

Crystal structure

Kimzeyite 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  = 12.456  Å , the natural mixed crystal from the type locality a  = 12.46 Å. Template: room group / 230

The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, zirconium (Zr 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

Kimzeyite is mainly formed in ultra-basic igneous and carbonatites at low pressure and high temperatures . Garnets rich in kimzeyite have also been found in contact metamorphic skarns .

Carbonatites

The Kimzeyite type locality is a carbonatite in the Kimzey Calcite Quarry (Calcite Hill) in the Magnet Cove Complex, Hot Spring County , Arkansas , USA . It occurs here in light areas of the carbonatite, which are associated with Ijolite . Besides calcite , accompanying minerals are apatite , monticellite , magnetite and perovskite, as well as vesuvianite , green mica , pyrite and, as an inclusion, anhydrite .

In the polino carbonatite near Terni in Umbria , Italy , kimzeyite occurs in the form of 10–25 µm large, roundish crystals in fine-grain calcite together with phlogopite, perovskite, monticellite and Fe-Ti oxides.

Basic igneous rocks

In the Shoshonite basalt of the 1975 eruption on Stromboli , Italy , kimzeyite occurs along with plagioclase , pyroxene , olivine , dark green spinel and monticellite .

The carbonate-rich areas of the lamprophyres of the Marathon Dikes at McKellar Harbor, Ontario , Canada contain kimzeyite- rich melanites along with olivine, phlogopite , andradite , calcite, perovskite, apatite and spinel.

Others

Kimzeyite occurs together with gehlenite , hercynite and pyrite in an ejecta from a pyroclastic stream near Anguillara Sabazia on Lake Bracciano north of Rome in Latium , central Italy .

See also

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n C. Milton, BL Ingram, LV Blade: Kimzeyite, a zirconium garnet from Magnet Cove, Arkansas . In: American Mineralogist . tape 46 , no. 5-6 , 1961, pp. 533-548 ( rruff.info [PDF; 987 kB ; accessed on August 5, 2017]).
  2. ↑ a b c d e Junji Yamakawa, Chiyoko Henmi, Akira Kawahara: Syntheses and X-ray studies of Kimzeyite, Ca3Zrs (Al, Fe) 2SiO12 . In: Mineralogical Journal . tape 16 , no. 7 , 1993, pp. 371–377 ( jst.go.jp [PDF; 659 kB ; accessed on August 5, 2017]).
  3. ↑ a b c d SM Antao and LA Cruickshank: Two cubic phases in kimzeyite garnet from the type locality Magnet Cove, Arkansas . In: Acta Crystallographica Section B . tape 72 , 2016, p. 846-854 ( iucr.org [accessed August 5, 2017]).
  4. ↑ a b List of localities for Kimzeyit in the Mineralienatlas and Mindat
  5. ^ A b Charles Milton, Lawrence V. Blade: Preliminary Note on Kimzeyite, a New Zirconium Garnet . In: Science . tape 127 , no. 3310 , 1958, pp. 1343 , doi : 10.1126 / science.127.3310.1343 .
  6. ↑ International Mineralogical Association: Commission on new minerals and mineral names: Report . In: Mineralogical Magazine . tape 36 , 1967, p. 131–136 ( rruff.info [PDF; 210 kB ; accessed on August 5, 2017]).
  7. ^ A b c 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]).
  8. ↑ a b Jun Ito and Clifford Frondel: Synthetic zirconium and titanium garnets . In: American Mineralogist . tape 52 , no. 5-6 , 1967, pp. 773–781 ( minsocam.org [PDF; 545 kB ; accessed on July 8, 2017]).
  9. ↑ a b c d Karl R. Whittle, Gregory R. Lumpkin, Frank J. Berry, Gordon Oates, Katherine L. Smith, Sergey Yudintsev, Nestor J. Zaluzec: The structure and ordering of zirconium and hafnium containing garnets studied by electron channeling , neutron diffraction and Mössbauer spectroscopy . In: Journal of Solid State Chemistry . tape 180 , 2007, p. 785-791 ( researchgate.net [PDF; 524 kB ; accessed on August 5, 2017]).
  10. ↑ FA Caporuscio, BL Scott, H. Xu, RK Feller: Garnet nuclear waste forms - Solubility at repository conditions . In: Nuclear Engineering and Design . tape 266 , 2014, p. 180–185 ( researchgate.net [PDF; 1.5 MB ; accessed on July 8, 2017]).
  11. ^ A b c d R. Grath Platt and Roger H. Mitchell: The Marathon Dikes. I: Zirconium-rich titanian garnets and manganoan magnesian ulviispinel-magnetite spinel . In: American Mineralogist . tape 64 , 1979, pp. 546-550 ( minsocam.org [PDF; 479 kB ; accessed on July 8, 2017]).
  12. ↑ a b c Emanuela Schingaro, Fernando Scordari, Flavio Capitanio, Giancarlo Parodi, David C. Smith, Annibale Mottana: Crystal chemistry of kimzeyite from Anguillara, Mts. Sabatini, Italy . In: European Journal of Mineralogy . tape 13 , no. 4 , 2001, doi : 10.1127 / 0935-1221 / 2001 / 0013-0749 .
  13. ^ A b Rosalba Munno, Giuseppe Rossi and Carla Tadini: Crystal chemistry of kimzeyite from Stromboli, Aeolian Islands, Italy . In: American Mineralogist . tape 65 , 1980, pp. 188–191 ( rruff.info [PDF; 523 kB ; accessed on July 8, 2017]).
  14. ↑ L. Lupini, CT Williams, AR Woolley: Zr-rich garnet and Zr and Th-rich perovskite from the carbonatite Polino, Italy . In: Mineralogical Magazine . tape 56 , 1992, pp. 581-586 ( rruff.info [PDF; 370 kB ; accessed on July 8, 2017]).