Calderite

from Wikipedia, the free encyclopedia
Calderite
Calderite garnet.jpg
Calderite crystals on matrix from Litzdalen in Sunndal ( Norway )
General and classification
chemical formula Mn 3 Fe 2 3+ [SiO 4 ] 3
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.AD.25 ( 8th edition : VIII / A.08)
51.4.3a.6
Similar minerals Garnet group
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  = natural: 11.81, synthetic: 11.821  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 7th
Density (g / cm 3 ) measured: 4.05; calculated: 4.07
Cleavage no
colour orange-yellow, dark yellow, reddish yellow, red-brown; yellow to greenish yellow in thin layers
Line color White
transparency transparent to translucent
shine Glass gloss
radioactivity no
Crystal optics
Refractive index n  = 1.875 natural, 1.970 (synthetic)
Birefringence none, as isotropic

Calderite is a rarely occurring mineral from the group of garnets within the mineral class of " silicates and germanates ". It crystallizes in the cubic crystal system with the idealized composition Mn 3 Fe 2 3+ [SiO 4 ] 3 , so from a chemical point of view it is a manganese - iron silicate, which structurally belongs to the island silicates .

Since Calderit mixed crystals with Spessartin (Mn 3 Al 2 [SiO 4 ] 3 ) and Andradit (Ca 3 Fe 2 [SiO 4 ] 3 forms), and therefore usually low levels of manganese by calcium and iron by aluminum replaced diadoch may be, the chemical formula generally also indicated with (Mn 2+ , Ca) 3 (Fe 3+ , Al) 2 [SiO 4 ] 3 .

Calderit is transparent to translucent and develops only small, glass shiny crystals of orange-yellow, dark yellow, reddish yellow or reddish-brown color. In thin layers it can also be yellow to greenish yellow. The mineral is usually found in the form of granular to massive mineral aggregates .

Etymology and history

Calderite was first scientifically described in 1909 by Lewis Leigh Fermor (1880-1954), who named the mineral after the geologist James Calder in recognition of his work on the geology of India.

The name calderite was also used for a rock ( Kut-Kumsany 12 miles NW of Hazareebagh ) and later for the mineral found there. The Anglo-Indian scientist Henry Piddington was the first to describe the calderite contained in rock samples from the rock. The samples that had been in the museum for some time were previously only referred to as undescribed Siliceo-Iron-and-Magnese Rock, from the district of Burdwan . The description of the mineral appeared in an 1851 article by Piddington in the Journal of the Asiatic Society of Bengal , with both Piddington and Calder being members of the Asiatic Society of Bengal.

classification

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

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Calderit belonged to the department of the "island silicates (nesosilicates)" where he collaborated with almandine, Andradite, Goldmanit, Grossular, Henritermierit , Hibschite , Holtstamit , Hydrougrandit , katoite , Kimzeyite , knorringite , majorite , morimotoite , pyrope , schorlomite , Spessartine, uwarowite , wadalite and yamatoite (discredited because it is identical to momoiite) the "garnet group" with system no. 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 calderite in the category 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 further anions; Cations in octahedral [6] and usually greater coordination "can be found, where together with almandine, andradite, goldmanite, grossular, henritermierite, holtstamite, katoite, kimzeyite, 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 mainly used in the English-speaking area , also classifies calderite in the “island silicate minerals ” section. Here it is together with pyrope, almandine, spessartine, knorringite and majorite in the "garnet group (pyralspite series)" with the system no. 51.04.03a to be found in the subsection “ Island silicates: SiO 4 groups only with cations in [6] and> [6] coordination ”.

Chemism

Calderite with the idealized composition [X] Mn 2+ 3 [Y] Fe 3+ [Z] Si 3 O 12 is the iron analog of spessartine ( [X] Mn 2+ 3 [Y] Al [Z] Si 3 O 12 ) or the manganese analog of andradite ( [X] Ca 3 [Y] Fe 3+ [Z] Si 3 O 12 ) with which it forms mixed crystals according to the exchange reactions

  • [Y] Fe 3+ = [Y] Al 3+ , (Spessartine),
  • [X] Mn 2+ = [X] Ca 2+ (andradite),

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

Pure calderite has not yet been found in nature and many finds called calderite are strictly speaking only mixed crystals containing calderite, e.g. B. Andradite. The information on the calderite content of complex manganese garnets from different publications is not always directly comparable, as it depends on the type of calculation. A composition can be described with different combinations of end links and the resulting calderite content can differ considerably.

The mixture of calderite with spessartine and andradite in the ratio 1: 1 corresponds to a mixture of calderite with grossular according to the coupled substitution

  • [X] Mn 2+ + [Y] Fe 3+ = [X] Ca 2+ + [Y] Al 3+ .

End link ratios based on grossular and Spessartine or almandine lead to higher calderite contents.

Depending on the description of a mixed crystal, a garnet rich in manganese can be either calderite or z. B. Andradite be addressed; a site like Otjosondu in Namibia is consequently either a type locality of calderite or not.

The following composition is given for the calderite from the type localities:

  • Wabush (Labrador): [X] (Mn 2.20 Ca 0.82 ) [Y] Fe 3+ 2.02 [Z] Si 4+ 3 O 12
  • Otjosondu (Namibia): [X] (Mn 1.96 Ca 1.09 ) [Y] (Fe 3+ 1.04 Al 3+ 0.87 Mg 2+ 0.07 Ti 4+ 0.01 ) [Z] (Si 4+ 2.97 Al 3+ 0.03 ) O 12 ,

A later, more detailed investigation of calderites from Otjosondu revealed calderite contents of only 22 - 36 mol%, calculated with andradite and spessartine. These Otjosondu grenades are calderite-rich andradites (48 - 68 mol%). Even a calculation with grossular only changes the ratios significantly for one sample, since the Spessartine content is otherwise too low.

Synthetic calderite contains a few mol% of the hypothetical end link blythite ( [X] Mn 2+ 3 [Y] Mn 3+ [Z] Si 3 O 12 ) according to the exchange reaction

  • [Y] Fe 3+ = [Y] Mn 3+ (blythite).

In the calderite-rich andradites from Otjosondu, Mn 3+ was detected directly spectroscopically in natural garnets on the octahedral Y-position . These natural garnets also contain 1 - 5 mol% of Blythite manganese in two different oxidation states.

Crystal structure

Calderite 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 Otjosondu has the lattice parameter a  = 11.81  Å . For synthetic calderite, a  = 11.821 Å or a  = 11.82239 Å was measured. Template: room group / 230

The structure is that of garnet . Manganese (Mn 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, iron (Fe 3+ ) the octahedral Y position surrounded by 6 oxygen ions and the tetrahedral Z position surrounded by 4 oxygen ions is exclusively silicon (Si 4+ ) occupied.

Education and Locations

Grainy calderite aggregate from Otjosondu, Otjozondjupa , Namibia ( overall size : 6 × 5.5 × 4.2 cm)

Calderite- rich garnets form in the pressure-stressed metamorphosis of manganese and iron-rich sediments under oxidizing conditions and occur together with aegirine , cutnohorite , hematite , pyrolusite , quartz , rhodonite and rhodochrosite .

Pure calderite is only stable at high pressures above 20–30 kBar at 700–900 ° C. This pressure-temperature range of the eclogite facies is reached in nature in subduction zones . At lower pressure or higher temperatures, pure calderite is broken down into pyrox mangite and magnetite . The degradation reaction is strongly dependent on the composition of the garnet and calderite-andradite-spessartine mixed crystals are already stable under the conditions of the amphibolite facies . This could also be confirmed for garnets with 60-80 mol% calderite and calderite is no longer recommended as an index mineral for high pressures.

As a rare mineral formation, calderite has so far (as of 2018) only been detected at 16 sites. The type locality is the Wabush iron formation in the Labrador area in Canada and Otjosondu in the Namibian region of Otjozondjupa . They are also the only known sites in these states so far.

In Otjosondu, calderite-rich garnet occurs together with hematite , quartz , hyalophane and apatite .

In Wabush calderite-rich garnet is found together with rhodonite and kutnahorite as well as aegirine, rhodonite and rhodochrosite.

In Europe, the mineral could be found in Italy ( Saint-Marcel (Aostatal) , Valtournenche (valley) ), Romania ( Iacobeni (Sibiu) ), Sweden ( Pajsberg / Filipstad ) and Switzerland ( Ferreratal ).

Calderit also appeared at Katkamsandi ( Jharkhand ) and Netra ( Madhya Pradesh ) in India and at Aggeneys ( North Cape ) in South Africa.

use

Pure calderite is only stable at pressures above 30 kbar. However, its proportion increases continuously with increasing pressures in the garnet solid solution, which is why it is well suited as a geobarometer .

literature

  • LL Fermor: The manganese-ore deposits of India . in: I. Introduction and mineralogy: Calderite, Memoirs of the Geological Survey of India , Volume 37 (1909), pp. 182–186 ( PDF 254.2 kB )
  • LL Fermor: On the composition of some Indian garnets , in: Records of the Geological Survey of India , Volume 59 (1927), pp. 191–207 ( PDF 1.98 MB )

Web links

Commons : Calderite  - collection of images, videos and audio files

Individual evidence

  1. ^ A b c Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  541 .
  2. ↑ a b c d e f Dominique Lattard and Werner Schreyer: Synthesis and stability of the garnet calderite in the system Fe Mn Si - O * . In: Contributions to Mineralogy and Petrology . tape 84 , 1983, pp. 199–214 ( researchgate.net [PDF; 1.9 MB ; accessed on April 28, 2018]).
  3. ↑ a b c d e f g Pete J. Dunn: On the Validity of Calderite . In: Canadian Mineralogist . tape 17 , 1979, pp. 569–571 ( rruff.info [PDF; 199 kB ; accessed on April 28, 2018]).
  4. ↑ a b Calderite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.5 kB )
  5. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  6. ^ Journal of the Asiatic Society of Bengal. Volume 19, 1851, pp. 145–148 ( online on Google Books )
  7. ^ 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]).
  8. ↑ a b Cornelis Klein, Jr .: Mineralogy and Petrology of the Metamorphosed Wabush Iron Formation, Southwestern Labrador . In: Journal of Petrology . tape 7 , 1966, pp. 246-305 , doi : 10.1093 / petrology / 7.2.246 .
  9. ↑ a b c d Georg Amthauer, Kerstin Katz-Lehnert, Dominique Lattard, Martin Okrusch and Eduard Woermann: Crystal chemistry of natural Mn3 + -bearing calderite-andradite garnets from Otjosondu, SW A / Namibia . In: Journal of Crystallography . tape 189 , 1989, pp. 43–56 ( researchgate.net [PDF; 693 kB ; accessed on April 28, 2018]).
  10. ↑ F. Alex Cevallos and RJ Cava: Comparison of the Magnetic properties of Mn3Fe2Si3O12 as a crystalline garnet and as a glass . In: Preprint on arxiv.org . 2018 ( arxiv.org [PDF; 696 kB ; accessed on April 29, 2018]).
  11. ↑ a b Maximilian Glas et al .: Granat . In: Christian Weise (ed.): ExtraLapis . tape 9 . Christian Weise Verlag, 1995, ISBN 3-921656-35-4 , ISSN  0945-8492 , p. 4 .
  12. ↑ Eric J. Essene: CRITICAL EVALUATION OF THE HIGH-PRESSURE STATUS OF CALDERITE, MN3FE2SI3O12 . In: Geological Society of America Abstracts with Programs . tape 38 , 2006, p. 208 ( confex.com [accessed April 29, 2018]).
  13. ↑ Mindat - Number of localities for calderite
  14. ↑ AR CABRAL, JM MOORE, BS MAPANI, M. KOUBOVÁ AND C.-D. SATTLER: GEOCHEMICAL AND MINERALOGICAL CONSTRAINTS ON THE GENESIS OF THE OTJOSONDU FERROMANGANESE DEPOSIT, NAMIBIA: HYDROTHERMAL EXHALATIVE VERSUS HYDROGENETIC (INCLUDING SNOWBALL-EARTH) ORIGINS . In: SOUTH AFRICAN JOURNAL OF GEOLOGY . tape 114 , 2011, pp. 57-76 ( researchgate.net [PDF; 3.9 MB ; accessed on May 2, 2018]).
  15. ↑ a b Mindat - Calderite
  16. ↑ GeoDZ.com The Lexicon of the Earth - Geobarometer