Zemkorite

from Wikipedia, the free encyclopedia
Zemkorite
General and classification
other names

IMA 1985-041

chemical formula
  • Na 2 Ca (CO 3 ) 2
  • (Na 1.8 K 0.2 ) Ca [CO 3 ] 2
Mineral class
(and possibly department) 		Carbonates and nitrates - carbonates without additional anions; without H 2 O
System no. to Strunz
and to Dana 		5.AC.10 ( 8th edition : V / B.05-020 (Lapis))
03/14/03/02
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m , ditrigonal dipyramidal; 6 m 2 or dihexagonal pyramidal; 6 mm
Space group P 6 3 / mmc (No. 194) , P 6 2 c (No. 190) or P 6 3 mc (No. 186)Template: room group / 194Template: room group / 190Template: room group / 186
Lattice parameters a  = 10.06  Å ; c  = 12.72 Å
Formula units Z  = 8
Physical Properties
Mohs hardness 2
Density (g / cm 3 ) 2.46 (measured); 2.47 (calculated)
Cleavage very perfectly parallel to the plane of the board
Break ; Tenacity brittle; not given
colour colorless
Line color White
transparency transparent
shine Glass to mother-of-pearl gloss
Crystal optics
Refractive indices n ω  = 1.535
n ε  = 1.513
Birefringence δ = 0.022
Optical character uniaxial negative
Pleochroism none
Other properties
Chemical behavior Easily soluble in warm water

Zemkorite is a very rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates ). It crystallizes in the hexagonal crystal system with the idealized chemical composition Na 2 Ca (CO 3 ) 2 - is thus seen a chemically sodium - calcium - carbonate .

Zemkorite was found in drill cores in the form of up to 4 mm large, fan-shaped mineral aggregates made of xenomorphic crystals up to 0.5 mm in size, granular and massive in narrow passages and as a filling in fracture cracks.

Its type locality is the Kimberlitschlot Udachnaya pipe ( Russian Трубка Удачная ) (also Udachnaya-Vostochnaya pipe; Udachnaya Pipe) at udachny ( coordinates of the Kimberlitschlotes Udachnaya pipe ) on the Wiljuiplateau the river Daldyn , Rayon Mirny (Sacha) , Federation subject Sacha (Jakutien), Russia .

Etymology and history

The mine Udachnaya pipe in Siberia - seen here from a helicopter - is the type locality of Zemkorirs and represents the largest diamond deposit in Russia

The locality "Udatschnaja" consists of two penetrating kimberlite vents that cut through Lower- Ordovician limestones . It was discovered in 1955 and diamond mining began in 1971. The chimneys contain eclogites , dunites and peridotite - xenolites and are mined in an open pit mine that is now more than 600 m deep. At the beginning of the 1980s, a previously unknown phase that was chemically very similar to Nyerereit was identified in kimberlite drill cores from a depth of 400 to 450 m in the eastern part of the Udachnaya twin chimney ("Udachnaya-Vostochnaya") . The kimberlite containing the examined mineral was completely untouched by serpentination processes and was described as unchanged.

After appropriate analyzes, it turned out that this phase is a new alkali - alkaline earth carbonate. The new mineral was submitted to the International Mineralogical Association (IMA), which recognized it on August 28, 1986 under the provisional designation "IMA 1985-041". The first scientific description of this mineral took place in 1988 by a team of Soviet scientists with KN Jegorow, Sinaida F. Uschtschapowskaja, AA Kaschajew, GV Bogdanow and Ju. I. Sisych in the Soviet science magazine Doklady Akademii Nauk SSSR ("Transactions of the Soviet Academy of Sciences"). The authors named the new mineral after the institute where the new mineral had been investigated, the "Institute of the Earth's crust" of the Siberian Branch of the Academy of Sciences of the USSR ( Russian Институт земной коры Сибирского отделения Российской академии наук ) and after Russian кора Земная for "earth crust" as Zemkorite ( Russian Земкорит , English Zemkorite ).

The type material for Zemkorite is stored under the catalog number 87573 in the systematic collection of the Mineralogical Museum " Alexander Evgenjewitsch Fersman " of the Russian Academy of Sciences in Moscow .

classification

The 8th edition of the mineral classification according to Strunz , which is now outdated, but still in use in some cases, does not yet list the Zemkorit. It would belong to the common mineral class of "carbonates, nitrates and borates" and to the department of "carbonates", where together with Burbankit , Bütschliit , Carbocernait , Eitelite , Fairchildit , Sahamalith and Shortit, it forms the "Eitelite Sahamalith Group" with the System no. Vb / A.05 within the sub-section “Anhydrous carbonates without foreign anions ”.

In the last revised and updated Lapis mineral directory in 2018 , which is still based on this outdated system of Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral was given the system and mineral number. V / B.05-055 . In the “Lapis system” this corresponds to the section “Anhydrous carbonates [CO 3 ] 2− , without foreign anions ”, where zemkorite, together with juangodoyite , Eitelite , Nyerereit, Gregoryite , Fairchildite , Bütschliit and Shortit, form the unnamed group V / B. 05 forms.

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, assigns the Zemkorite to the “carbonates and nitrates” class, which has been reduced by borates, and to the “carbonates without additional ones” Anions; without H 2 O “. This is further subdivided according to the group affiliation of the cations involved , so that the mineral can be found according to its composition in the subsection "Alkali and alkaline earth carbonates", where, together with Nyerereit, the unnamed group with the system no. 5.AC.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the zemkorite to the common class of “carbonates, nitrates and borates” and there in the department of “carbonates”, like the outdated Strunzian system. Here he is together with Fairchildit in the " Fairchildit group " with the system no. 03/14/03 within the sub-section “Anhydrous carbonates with a compound formula A + B 2+ (CO 3 ) 2 ”.

Chemism

Mean values from two microprobe analyzes on Zemkorite grains from the type locality yielded 25.72% Na 2 O; 0.05% Al 2 O 3 ; 6.40% K 2 O; 28.39% CaO; and 39.20% CO 2 (determined wet-chemically); Total 99.76%. MgO, SiO 2 ; TiO 2 ; Contents of MnO, FeO, BaO and SrO were not detectable. The empirical formula (Na 1.80 K 0.29 ) Σ = 2.09 Ca 1.10 (CO 3 ) 1.93 , which results in Na 2 Ca (CO 3 ) 2, is calculated from the values ​​determined during the analyzes can be simplified. This simplified formula requires 30.08% Na 2 O; 27.21% CaO; and 42.71% CO 2 .

The official formula of the IMA for the Zemkorite corresponds to the spelling of Jegorow and colleagues and is given as Na 2 Ca (CO 3 ) 2 . The formula notation according to Strunz is (Na 1.8 K 0.2 ) Ca [CO 3 ] 2 and corresponds roughly to the empirical formula of Jegorow and colleagues. As usual, the anion association is summarized here in square brackets.

The sole element combination Na-Ca-CO point among the currently known minerals (as of 2020) in addition to Zemkorite only Shortite , Na 2 Ca 2 (CO 3 ) 3 , and Nyerereite , Na 2 Ca (CO 3 ) 2 , and the three unnamed phases Unnamed (Na-Ca Carbonate I) , Na 4 Ca (CO 3 ) 3 , Unnamed (Na-Ca Carbonate II) , Na 2 Ca 3 (CO 3 ) 4 , and Unnamed (Na-Ca Carbonate III) , Na 2 Ca 4 (CO 3 ) 5 .

The chemical compound Na 2 Ca (CO 3 ) 2 is dimorphic and could even be trimorphic, since the nature of the “natrofairchildite” from the alkaline rock-ultrabasite massif “Vuoriyärvi” is still not fully understood. Zemkorite is the hexagonal dimorph to the orthorhombic Nyerereit. The high temperature modification β-Nyerereit is like the Zemkorite hexagonal, but only stable at a temperature of over 340 ° C.

From a chemical point of view, Zemkorite is the Na-dominant analogue of the K-dominated Fairchildite , with which it probably forms a mixed crystal row , as the empirical formulas of the current species suggest.

Crystal structure

Zemkorite crystallizes in the hexagonal crystal system in the space group P 6 3 / mmc (space group no.194 ) , space group P 6 2 c (space group no.190) or space group P 6 3 mc (space group no.186) with the lattice parameters a = 10.06  Å and c = 12.72 Å as well as eight formula units per unit cell . More recent data from Gopalakrishnarao Parthasarathy and colleagues provided very similar lattice parameters with a = 10.038  Å and c = 12.726 Å. Template: room group / 194 Template: room group / 190 Template: room group / 186

properties

morphology

Its type locality Zemkorite typically fills cracks in the thin unchanged kimberlite along the contacts between matrix and olivine - Xenoliths and - phenocrysts . The mineral forms tabular grains 0.1 to 0.5 mm in size, which do not reveal any crystal faces. Fan-shaped crystal aggregates in sizes from 3 to 4 mm, which sit in the spaces between large olivine insets , have also been identified very rarely .

Zemkorite from the kimberlite of "Venkatampalle" near Anantapur in the district of the same name , Andhra Pradesh, India, ( coordinates of the kimberlite chimney Venkatampalle ) is found in needle-like aggregates which, similar to the kimberlite chimney "Udachnaya", but much more frequently, come together to form fan-shaped aggregates.

physical and chemical properties

The crystals of the zemcorite are colorless or cream-colored, while their streak color is always white. The surfaces of the grains and aggregates, which are transparent according to the color of the mineral, show a characteristic glassy to mother-of-pearl-like sheen . According to this glass gloss, Zemkorite has a medium-high light refraction ( n ε  = 1.513; n ω  = 1.535) and a low birefringence (δ = 0.022). In transmitted light, the uniaxial negative zemcorite is colorless and shows no pleochroism .

Zemkorite shows a very perfect cleavage parallel to the table plane. The mineral is brittle and there is no information about its behavior in the event of breakage . Zemkorite has a Mohs hardness of 2 and is one of the soft minerals that can be scratched with the fingernail if the crystal size is appropriate, like the reference mineral gypsum . The measured density for Zemkorite is 2.46 g / cm³, the calculated density is 2.47 g / cm³.

The mineral is not in the long wavelength even in the short wavelength UV light , a fluorescent . Zemkorite is easily soluble in warm water. Kimberlite drill cores, which contain Zemkorite and Shortite and which have been lying in the open for a long time, easily transformed into a fine, loose mass under the influence of atmospheric substances .

Education and Locations

At its type locality, Zemkorite represents a postmagmatic formation. It was formed when the kimberlite was overprinted by highly mineralized, sodium-rich solutions that were formed when the rocks of the Udachnaya chimney interact with brines near the surface from the sub-Cambrian side rock. Zemkorite from the "Venkatampalle" kimberlite chimney comes from the crumbly "Yellow Ground" at a depth of ≈ 4 m; the hard “blue ground” only occurs here at ≈ 10 m. The kimberlite is coarse-grained and unevenly mixed with xenolithic rock fragments and xenolithic minerals.

Accompanying minerals of the Zemkorite at its type locality are shortite and rarely also halite . Shortite often forms in fine cracks in the Zemkorite in the form of small, finely crystalline aggregates. Occasionally, relics of the Zemkorite are still observed in the cryptocrystalline, powdery masses of the white shortite. In the material from the Indian kimberlite chimney "Venkatampalle", zemkorite is accompanied by altered olivine grains, phlogopite and indicator minerals such as pyrope with kelyphitic edges, picroilmenite (a variety of ilmenite rich in Mg ) with leucoxene membranes and diopside of the chromium diopside variety .

Since zemkorite consists mainly of sodium, but has a significant proportion of calcium and is also a carbonate mineral, its formation is probably not postmagmatic, but rather occurred in the late stages of kimberlite formation through decompression melting and the separation of a sodium carbonate melt by immiscible liquids. The estimate of 700  K for the upper thermal stability limit of Zemkorite only marginally exceeds the thermal stabilities of Na-K-Ca-carbonate mineral mixed crystals in the pure Na 2 CO 3 -K 2 CO 3 -CaCO 3 system and is comparable with the estimates by Joseph Pyle and Stephen Haggerty for eclogites of the upper mantle . It is also possible that Zemkorite was obtained in the Indian kimberlite chimney "Venkatampalle" directly from metasomatic fluids or by decomposition of one of the components of a sodium carbonate association from the upper mantle. Such a component could be the devitrified Na-rich glass with up to 5 wt .-% CaO described by Pyle and Haggerty .

As an extremely rare mineral formation, Zemkorite (as of 2020) is only known from five other sites in addition to its type locality. The type locality of Zemkorits is the eastern Kimberlitschlot Udachnaya pipe ( Russian Трубка Удачная ) (Udachnaya-Vostochnaya pipe) at udachny on the Wiljuiplateau the river Daldyn , Rajon Mirny (Sacha) , federal subject Sacha (Yakutia), Russia .

Other locations for Zemkorite are:

Locations for Zemkorite from Germany , Austria and Switzerland are therefore unknown.

use

Due to its rarity, Zemkorite is completely insignificant from an economic point of view.

See also

literature

  • KN Jegorow, Sinaida F. Uschtschapowskaja, AA Kaschajew, GV Bogdanow, Ju. I. Sisych: Земкорит - новый карбонат из кимберлитов Якутии (Zemkorite - a new carbonate from the Yakutian kimberlites) . In: Doklady Akademii Nauk SSSR . tape 301 , 1988, pp. 188–193 (Russian, rruff.info [PDF; 713 kB ; accessed on January 25, 2020]).
  • Zemkorite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 65 kB ; accessed on January 25, 2020]).

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao KN Jegorow, Sinaida F. Uschtschapowskaja, AA Kaschajew, GV Bogdanow, Ju. I. Sisych: Земкорит - новый карбонат из кимберлитов Якутии (Zemkorite - a new carbonate from the Yakutian kimberlites) . In: Doklady Akademii Nauk SSSR . tape 301 , 1988, pp. 188–193 (Russian, rruff.info [PDF; 713 kB ; accessed on January 25, 2020]).
  2. ↑ a b c d e Zemkorite. In: mindat.org. Hudson Institute of Mineralogy, accessed January 25, 2020 .
  3. ↑ a b c d Zemkorite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 65  kB ; accessed on January 25, 2020]).
  4. ↑ a b c d 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.  290 (English).
  5. ^ A b David Barthelmy: Zemkorite Mineral Data. In: webmineral.com. Retrieved January 25, 2020 .
  6. ^ Geology and Mineralogy of the Udachnaya open-pit mine. In: mindat.org. Hudson Institute of Mineralogy, accessed January 25, 2020 .
  7. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 25, 2019 .
  9. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: January 2020. (PDF; 1762 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, January 2020, accessed January 20, 2020 .
  10. ↑ Minerals with Na, Ca, O, C. In: mindat.org. Hudson Institute of Mineralogy, accessed January 25, 2020 .
  11. ↑ Michael Fleischer, George Y. Chao, Akiro Kato: New mineral names . In: American Mineralogist . tape 60 , no. 5-6 , 1975, pp. 485–489 (English, minsocam.org [PDF; 624 kB ; accessed on January 25, 2020]).
  12. ^ Duncan McKie, EJ Frankis: Nyerereite: A new volcanic carbonate mineral from Oldoinyo Lengai, Tanzania . In: Journal of Crystallography . tape 145 , no. 1-2 , 1977, pp. 73–95 , doi : 10.1524 / zkri.1977.145.1-2.73 (English, rruff.info [PDF; 1,2 MB ; accessed on December 4, 2019]).
  13. ↑ a b c d e f g h Gopalakrishnarao Parthasarathy, Talari Ramakrishnaiah K. Chetty, Stephen E. Haggerty: Thermal stability and spectroscopic studies of zemkorite: A carbonate from the Venkatampalle kimberlite of southern India . In: The American Mineralogist . tape 87 , no. 10 , 2002, p. 1384–1389 , doi : 10.2138 / am-2002-1014 (English, rruff.info [PDF; 454 kB ; accessed on January 25, 2020]).
  14. ^ Alan F. Cooper, John Gittins, Orville Frank Tuttle : The system Na 2 CO 3 -K 2 CO 3 -CaCO 3 at 1 kilobar and its significance in carbonatite petrogeneses . In: American Journal of Science . tape 275 , no. 5 , 1975, p. 534-560 , doi : 10.2475 / ajs.275.5.534 (English).
  15. ↑ a b Joseph M. Pyle, Stephen E. Haggerty: Silicate-carbonate liquid immisibility in upper-mantle eclogites: implications for natrosilicic and carbonatitic conjugate melts . In: Geochimica Cosmochimica Acta . tape 58 , no. 14 , 1994, pp. 2997-3011 , doi : 10.1016 / 0016-7037 (94) 90174-0 (English).
  16. ↑ Localities for Zemkorite. In: mindat.org. Hudson Institute of Mineralogy, accessed January 25, 2020 .
  17. ↑ a b c List of places where Zemkorite was found in the Mineralienatlas and Mindat (accessed on January 25, 2020)