Roedderite

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Roedderite
Roedderite.jpg
Yellow Roedderite crystals from Ettringer Bellerberg , Eifel, Germany
General and classification
other names

IMA 1965-023

chemical formula
  • K [12] (NaH 2 O) 2 [9] (Mg, Fe) 2 [6] Mg 3 [4] [Si 12 O 30 ]
  • KNaMg 2 (Mg 3 Si 12 ) O 30
  • (K, Na) NaMg 5 Si 12 O 30
Mineral class
(and possibly department) 		Silicates and germanates - ring silicates
System no. to Strunz
and to Dana 		9.CM.05 ( 8th edition : VIII / E.22)
63.02.01a.14
Similar minerals Cordierite , Osumilite , Chayesite
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol ditrigonal-dipyramidal; 6 m 2
Space group P 6 2 c (No. 190)Template: room group / 190
Lattice parameters a  = 10.141  Å ; c  = 14.286 Å
Formula units Z  = 2
Twinning -
Physical Properties
Mohs hardness 6.5
Density (g / cm 3 ) measured: 2.6; calculated: 2.63
Cleavage is missing
colour colorless
Line color not determined
transparency Please complete!
shine not specified
Crystal optics
Refractive indices n ω  = 1.537
n ε  = 1.542
Birefringence δ = 0.005
Optical character uniaxial positive

The mineral roedderite is a very rarely occurring ring silicate from the milarite group with the idealized chemical composition K Na Mg 5 Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops colorless to blue colored, platy to prismatic crystals, usually less than a millimeter in size.

Roedderite is found in small amounts in chondritic meteorites , in aubrites , in interstellar dust and comets as well as in foreign rock inclusions in basaltic magmas from various volcanoes in the Eifel , Germany , the basalt quarry near Klöch in Burgenland , Austria and some volcanoes in Auvergne , France .

Etymology and history

Edwin Woods Roedder (1919-2006) was the first to describe a compound with the composition K 2 Mg 5 Si 12 O 30 in 1951 during the systematic investigation of the compounds in the K 2 O — MgO — SiO 2 system . The Na analogue Na 2 Mg 5 Si 12 O 30 was synthesized by Schairer, Yoder and Keene 3 years later.

The mineral roedderite was discovered in 1966 by Luis H. Fuchs, Clifford Frondel and Cornelis Klein, Jr. in the Indarch meteorite, an enstatite chondrite that fell on April 7, 1891 near Shusha in Azerbaijan . The new mineral of the milarite group was named after Edwin Woods Roedder.

The first terrestrial occurrence of roedderite, silicate-rich xenolites in a basalt from the Laacher volcanic area in the Eifel, was described by Hentschel, Abraham, Schreyer 1977.

classification

In the outdated, but still partially common 8th edition of the mineral classification by Strunz Roedderit belongs Almarudit , Armenit , Berezanskit , Brannockit , Darapiosit , Dusmatovit , Emeleusit , Faizievit , Merrihueit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Sogdianit , Sugilite and Yagiit to the general division of " ring silicates (cyclosilicates)" in the " milarite-osumilite group " with system no. VIII / E.22 .

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies roedderite in the "ring silicates" section. This is, however, further subdivided according to the structure of the rings, so that the mineral can be found in the sub-section "[Si 6 O 18 ] 12− -six double rings" according to its structure . In it it belongs with Agakhanovit-Ce , Almarudit, Armenit, Berezanskit, Brannockit, Eifelit , Chayesit , Darapiosit, Dusmatovit, Friedrichbeckeit , Klöchit , Merrihueit, Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudrettogit, Trattnerite , Shibdiankovit , Soudrettogit Sugilite and Yagiite to the " milarite group " with the system no. 9.CM.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns roedderite to the class of "silicates and germanates", but there in the more finely divided division of "ring silicates: condensed rings". Here it is in the " Milarite Osumilith Group (Milarite Osumilith Subgroup) " with the system no. 63.02.01a can be found in the subsection “ Ring Silicates : Condensed, 6-membered Rings”.

Chemism

Roedderite is the Mg 2+ analog of Merrihueit and forms unbroken rows of mixed crystals with Merrihueit, Eifelite and Chayesite according to the exchange reactions:

  • [A, T2] Mg 2+ = [A, T2] Fe 2+ (Merrihueit)
  • [B] □ + [A] Mg 2+ = [B] Na + + [A] Na + (Eifelite)
  • [B] Na + [T2] Mg 2+ = [B] □ + [T2] Fe 3+ (chayesite)

The measured composition from the type locality is [C, B] (K 1.30 Na 0.69 ) [A, T2] (Mg 4.86 Fe 2+ 0.27 ) [T1] [Si 11.88 Al 0, 07 O 30 ], where the positions in the crystal structure are indicated in square brackets .

Crystal structure

Roedderite crystallizes in the hexagonal crystal system in the space group P 6 2 c (space group no. 190) with the lattice parameters a  = 10.141  Å and c  = 14.286 Å as well as two formula units per unit cell . Template: room group / 190

Roedderite is isotypic to milarite , i.e. H. it crystallizes with the same structure as milarite.

The T1 position is split into two sub-positions T1 and T11, which build up the 6-double rings and both are fully occupied with silicon (Si 4+ ).

The 12-fold coordinated C position is fully occupied with potassium and some sodium.

The 9-fold coordinated B-position is split into two positions and contains Na, which is incorporated almost completely in an orderly manner on the B1-position, which is half occupied. The B2 position is almost empty.

The T2 and A positions are completely occupied by magnesium and small amounts of iron.

Education and Locations

Roedderite forms at very high temperatures around 900 to 1000 ° C and at low pressure. Under extremely low-oxygen (reducing) conditions such as B. in meteorites the iron is only in metallic form and almost iron-free rodderite can also form in an iron-rich environment.

Under oxidizing conditions such as B. in many volcanic rocks there is iron as Fe 3+ and in an iron-containing environment roedderite- chayesite mixed crystals form. Pure roedderite then only forms in an iron-free environment such as B. some xenolites in the basaltic magmas of the Eifel volcanoes.

stability

Only the stability of synthetic Na-free K-Roedderite (K 2 Mg 5 Si 12 O 30 ) has been investigated experimentally . In the presence of water, its stability field is limited to high temperatures at low pressure. At temperatures below a line from 595 ° C / 1 kbar to 820 ° C / 6.5 kbar, K-Roedderite is degraded to mica (K Mg 2.5 Si 4 O 10 (OH) 2 ) and quartz. At temperatures above a line from 820 ° C / 6.5 kbar to approx. 1100 ° C / 1 kbar , roedderite melts incongruently with forsterite and melt .

If the composition of the rock deviates from the Roedderite composition, its stability field is reduced. K- Richterit z. B. is stable up to 1000 ° C and decomposes at a pressure below 150 bar to K-Roedderite, K-Mg-Silicate, Forsterite, Diopside, steam and melt. At higher pressure, roedderite no longer occurs here.

In an anhydrous environment, K-Roedderit is still stable at 35 kbar. Since no water-containing compounds such as mica or Richterite can form, K-Roedderite occurs at lower temperatures. The melting reactions also shift to higher temperatures.

Meteorites

Roedderite occurs in silicate inclusions of chondritic meteorites , iron meteorites and in aubrites .

In the Kaidun meteorite, which fell on December 3, 1980 south of Budah, Hadramaut Governorate , Yemen , roedderite occurs in silicate inclusions together with SiO 2 , glass with an albitic composition, enstatite and Na 2 S 2 .

Enstatite chondrites

In its type locality , the Indarch meteorite, an enstatite chondrite from the class EH4, roedderite occurs together with enstatite , clinoenstatite, albite , tridymite , troilite , Ni-iron, writersite , oldhamite and amorphous carbon .

In Quingzhen EH3 Chondrit Roedderit be associated with SiO 2 and albite in silicate inclusions in kamazite -, Troilit- oldhamite aggregates in passages in troilite, kamazite, Perryite and schreibersite as well as elongated small crystals in niningerite , preferably on contact with troilite.

In the Mezö-Madaras meteorite ( Mădăraş , Mureş County ( Transylvania ), Romania ), an unequelibrated L3 chondrite meteorite, roedderite and merrihuetite were found as inclusions in enstatite. Other accompanying minerals are troilite and SiO 2 .

In the L3.5 chondrite ALHA-77011 iron-containing roedderite occurs together with enstatite SiO 2 and troilite. In LL3.7 Chondrite ALHA-77278, roedderite is associated with pyroxene, SiO 2 , olivine and troilite.

Aubrite:

In the Bustee Meteorite, Gorakhpur , Basti District, Basti Division, Uttar Pradesh , India , roedderite occurs together with forsterite and diopside.

In the Peña Blanca Spring Aubrit, one to two millimeter large roedderite crystals are framed and partially replaced by diopside, albite and enstatite.

In the aubrite meteorite Yamato-793592 from the Antarctic, roedderite was found in the finely crystalline base mass together with enstatite, diopside, forsterite, plagioclase, SiO 2 , glass, nickel-iron, writersite, troilite, alabandin, daubréelite, djerfisherite and Na-Cr sulfide found.

The Khor Temiki meteorite, which fell on April 18, 1932 near Oleb in the Gash Delta, Wilayah Kassala , Sudan, and the Antarctic meteroites from Lewis Cliff, Buckley Island quadrangle LEW-87020 and LEW-87294 also contain roedderite.

Iron meteorites:

In the Wichita County Meteorite, Wichita County (Texas) , USA, an IA iron meteorite, roedderite is found in silicate inclusions together with forsterite , albite , Richterite , whitlockite , graphite and crinovite .

In the Canion Diabolo IA iron meteorite, roedderite occurs together with uryite , Richterite, chromite , sphalerite , troilite, graphite and crinovite.

In the San Cristobal IAB iron meteorite, roedderite was detected together with olivine, orthopyroxene, plagioclase and phosphates in silicate inclusions.

Comets

Material from comet 81P / Wild 2 , which brought the Stardust space probe to Earth, contained roedderite along with melilite , anorthite , corundum and osbornite . These minerals are typical of chondritic meteorites and are formed in the inner solar nebula , but are absent in the interplanetary dust. Their appearance in comets is taken as an indication of a large-scale mixing of the solar nebula.

In 2014, porous, chondritic micrometeorites were recovered from the Antarctic snow and ice that resemble samples of interplanetary dust particles collected by aircraft in the stratosphere . These dust particles represent the most pristine material from the time our solar system was formed and, in addition to enstatite and cosmochlor, also contained roedderite.

Contact metamorphic pelite

Roedderite is formed during the contact metamorphosis of xenolites that are low in aluminum and iron by basaltic magmas and is deposited directly from a gas phase rich in alkali, silicon and magnesium. This type includes sites in the Vulkaneifel , Germany , Burgenland , Austria and some volcanoes in Auvergne , France .

On the Stradner Kogel near Wilhelmsdorf (Eastern Styria), roedderite occurs in cavities of xenolites together with amphibole , enstatite , aegirine and tridymite .

See also

Web links

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

Individual evidence

  1. ^ Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  613 .
  2. ^ IMA / CNMNC List of Mineral Names; November 2017 (PDF 1.67 MB)
  3. ↑ a b c d e f g h i j k l m n o p q LH Fuchs, C. Frondel, C. Klein: Roedderite, a new mineral from the Indarch Meteorite . In: The American Mineralogist . tape 51 , no. 7 , July 1966, p. 949–955 ( available online at rruff.info [PDF; 447 kB ; accessed on March 9, 2019]).
  4. ↑ a b c d e f g h Thomas Armbruster: Crystal chemistry of double-ring silicates: structure of roedderite at 100 and 300 K . In: European Journal of Mineralogy . tape 1 , no. 5 , 1989, pp. 715-718 , doi : 10.1127 / ejm / 1/5/0715 .
  5. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  6. ↑ a b c d W. Hsu: Geochemical and petrographic studies of oldhamite, diopside, and roedderite in enstatite meteorites . In: Meteoritics & Planetary Science . tape 33 , 1998, pp. 291-301 , doi : 10.1111 / j.1945-5100.1998.tb01633.x .
  7. ↑ a b HA Ishii, JP Bradley, ZR Dai, M. Chi, AT Kearsley, MJ Burchell, ND Browning, F. Molster: Comparison of comet 81P / Wild 2 dust with interplanetary dust from comets . In: Science . tape 319 , January 25, 2008, p. 447–450 , doi : 10.1126 / science.1150683 ( available online at researchgate.net [PDF; 449 kB ; accessed on March 9, 2019]).
  8. ↑ a b T. Noguchi, N. Ohashi, S. Tsujimoto, T. Mitsunari, JP Bradley, T. Nakamura, S. Toh, T. Stephan, N. Iwata: Cometary dust in Antarctic ice and snow: Past and present chondritic porous micrometeorites preserved on the Earth's surface . In: Earth and Planetary Science Letters . tape 410 , January 15, 2015, p. 1–11 , doi : 10.1016 / j.epsl.2014.11.012 ( abstract ).
  9. ↑ a b Caspar Quarry, Bellerberg volcano, Ettringen, Mayen, Eifel, Rhineland-Palatinate, Germany
  10. ↑ a b c Karl Ettinger, Walter Postel, Josef Taucher, Franz Walter: Minerals of the Osumilith group (Roedderite, Merrihueit, Chayesite and Osumilith) from the Styrian-Burgenland volcanic area, Austria . In: Tschermaks mineralogical and petrographic communications . tape 31 , 1996, pp. 215–234 ( PDF on ZOBODAT [accessed March 9, 2019]).
  11. ^ Basalt quarry, Klöch, Bad Radkersburg, Styria, Austria
  12. ↑ a b Mont Denise, Espaly-Saint-Marcel, Le Puy-en-Velay, Haute-Loire, Auvergne, France
  13. ↑ Edwin Woods Roedder: The System K2O-MgO-SiO2. Part 1 . In: American Journal of Science . tape 249 , February 1951, p. 81–130 ( available online at primefan.ru [PDF; 7,8 MB ; accessed on March 9, 2019]).
  14. ↑ JF Schairer, HS Yoder, AG Keene: The systems Na2O-MgO-SiO2 and Na2O-FeO-SiO2 . In: Carnegie Inst. Washington, Yearbook . tape 53 , 1954, pp. 123-125 .
  15. ↑ G. Hentschel, K. Abraham, W. Schreyer: Roedderit and Osumilith from the Laacher volcanic area . In: Advances in Mineralogy . tape 55 , no. 1 , 1977, pp. 43-44 .
  16. ↑ a b c d G. Hentschel, K. Abraham, W. Schreyer: First terrestrial occurrence of roedderite in volcanic ejecta of the Eifel, Germany . In: Contributions to Mineralogy and Petrology . tape 73 , no. 2 , 1980, p. 127-130 , doi : 10.1007 / BF00371387 .
  17. ↑ a b E. Alietti, MF Brigatti, p Capredi, L. Poppi: The roedderite-chayesite series from Spanish lamproites: crystal-chemical characterization . In: Mineralogical Magazine . tape 58 , December 1994, p. 655–662 ( available online at rruff.info [PDF; 556 kB ; accessed on March 9, 2019]).
  18. ^ A b F. Seifert, W. Schreyer: Stability relations of K 2 Mg 5 Si 12 O 30 , and end member of the merrihueite-roedderite group of meteoritic minerals . In: Contributions to Mineralogy and Petrology . tape 22 , no. 3 , 1969, p. 190-207 , doi : 10.1007 / BF00387953 .
  19. ^ Robert W. Charles: The Phase Equilibria of Richterite and Ferrorichterite . In: American Mineralogist . tape 60 , 1975, pp. 367–374 ( available online at minsocam.org [PDF; 795 kB ; accessed on March 9, 2019]).
  20. ↑ AV Ivanov, GJ Macpherson, ME Zolensky, NN Kononkova, LF Migdisova: The Kaidun meteorite: Composition and origin of inclusions in the metal of an enstatite chondrite clast . In: Meteoritics & Planetary Science . tape 31 , 1996, pp. 621-626 , doi : 10.1111 / j.1945-5100.1996.tb02034.x .
  21. ↑ a b c d ER Rambaldi, RS Rajan: Roedderite in the Qingzhen (EH3) Chondrite . In: Meteoritics . tape 21 , no. 1 , March 31, 1986, pp. 141-149 , bibcode : 1986Metic..21..141R .
  22. ^ A b AN Krot, JT Wasson: Silica-merrihueite / roedderite-bearing chondrules and clasts in ordinary chondrites: New occurrences and possible origin . In: Meteoritics . tape 29 , no. 5 , September 1994, bibcode : 1994Metic..29..707K .
  23. ↑ TJ McCoy, ES Bullock: Volatile-rich phases in aubrites: Clues to understanding the mineralogy of Mercury? In: 78th Annual Meeting of the Meteoritical Society . 2015 ( available online at hou.usra.edu [PDF; 34 kB ; accessed on March 9, 2019]).
  24. ↑ M. Kimura, Y.-T. Lin, Y. Ikeda, A. El Goresy, K. Yanai, H. Kojima: Mineralogy of Antarctic aubrities, Yamato-793592 and Allan Hills-78113: Comparison with non-Antarctic aubrites and E-chondrites . In: Seventeenth Symposium on Antarctic Meteorites. Proceedings of the NIPR Symposium, No. 6, held August 19-21, 1992, at the National Institute of Polar Research, Tokyo. tape 6 , 1993, pp. 186–203 , bibcode : 1993AMR ..... 6..186K .
  25. ^ RA Fogel: The Composition of Roedderite in Aubrites . In: Meteoritics & Planetary Science . tape 37 , 2002, p. A48 , bibcode : 2002M & PSA..37Q..48F .
  26. ↑ Edwald Olsen: A new occurrence of roedderite and its bearing on osumilite-type minerals . In: The American Mineralogist . tape 52 , September 1967, p. 1519–1523 ( available online at minsocam.org [PDF; 335 kB ; accessed on March 9, 2019]).
  27. ↑ M. Prinz, CE Nehru, JS Delaney, M. Weisberg: Silicates in IAB and IIICD Irons, Winonaites, Lodranites an Brachina: a Primitive and Modified-Primitive Group . In: Lunar and Planetary Science . tape 14 , 1983, p. 616-617 , bibcode : 1983LPI .... 14..616P .