Zhemchuzhnikovit

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Zhemchuzhnikovit
General and classification
other names
  • Jemchuznikovite
  • Shemchushnikovit
  • Šemčušnikovit
  • Shemchushnikowit
chemical formula
  • NaMg (Fe 3+ 0.31 , Al 0.69 ) (C 2 O 4 ) 3 • 9H 2 O
  • NaMg (Al, Fe) (C 2 O 4 ) 3 · 8H 2 O
  • NaMg (Fe 0.4 Al 0.6 ) (C 2 O 4 ) 3 · 8-9H 2 O
Mineral class
(and possibly department) 		Organic compounds
System no. to Strunz
and to Dana 		10.AB.35 ( 8th edition : IX / A.01)
01.50.07.02
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-pyramidal; 3 m
Space group P 3 c 1 (No. 158)Template: room group / 158
Lattice parameters a  = 16.809  Å ; c  = 12.658 Å
Formula units Z  = 6
Frequent crystal faces {0001}, {11 2 0}, {22 4 1}
Physical Properties
Mohs hardness 2
Density (g / cm 3 ) 1.69 (measured); 1.66 (calculated), 1.64
Cleavage good after {0001}
colour green, smoke green in daylight, violet-amethyst-colored, greenish-yellow in artificial light
Line color probably white with shades of green
transparency semi-transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.479
n ε  = 1.408
Birefringence δ = 0.071
Optical character uniaxial negative
Pleochroism strong from O = greenish yellow to E = reddish violet
Other properties
Chemical behavior soluble in H 2 O, the solution has a pH of 5.51
Special features Alexandrite-like color change from daylight to artificial light

Zhemchuzhnikovit is a very rarely occurring mineral from the mineral class of " organic compounds ". It crystallizes in the trigonal crystal system with the chemical formula NaMg (Fe 3+ 0.31 Al 0.69 ) (C 2 O 4 ) 3 · 9H 2 O, ie chemically seen a crystal water-containing sodium - magnesium - aluminum - iron - oxalate .

Zhemchuzhnikovit of the type locality is found in thin Gängchen in lignite consisting of acicular to fibrous aggregates isometric and very rarely from about 0.05 mm large crystals exist. The mineral comes from the "Chai-Tumus" (Tschaitumususk) coal deposit located 200 km south of the estuary of the Lena River in the Sakha Republic (Yakutia) , Far East Federal District in Siberia , Russia .

Etymology and history

The Russian mineralogist PI Glushinsky, who found the mineral in 1956, is considered the discoverer of zhemchuzhnikovite. The first brief characterization was carried out by Yevgeny Iwanowitsch Nefedow in 1960, a more detailed description was published by the Russian mineralogists Juri N. Knipowitsch , AI Kombow and Evgeni Iwanowitsch Nefedow in 1963. They named the mineral after the Russian clay mineralogist Yuri Apollonowitsch Shemchushnikow (1885–1957) ), a specialist in coal geology and petrology at the All-Russian Geological Research Institute (WSEGEI) Alexander Petrovich Karpinsky (WSEGEI) in Leningrad (St. Petersburg). After these two publications, little was published about the new mineral, and the crystal structure of the zhemchuzhnikovite has never been described. It was only in 2016, when it was discovered that the mineral structural similarities with man-made metal-organic frameworks (English: metal-organic frameworks, MOFs), knows which one as magnetic and proton-conductive metal oxalates, which led to a re-examination of Zhemchuzhnikovit ( and the chemically closely related stepanovite). In the course of this, the information on the physical and crystallographic properties of the mineral were checked and the structure of the mineral clarified.

The type material for zhemchuzhnikovit is listed under catalog no. 1955/1 kept in the collection of the Mining Institute in St. Petersburg , Russia .

classification

In the now outdated, but still in use 8th edition of the mineral systematics according to Strunz , the zhemchuzhnikovite belonged to the mineral class of "organic compounds" and there to the department of "salts of organic acids", where together with Caoxit , Coskrenit- (Ce) , Glushinskit , Humboldtin , Levinsonite (Y) , Lindbergite , Minguzzite , Moolooite , Natroxalate , Novgorodovaite , Oxammite , Stepanovite , Weddellite , Wheatleyite , Whewellite and Zugshunstit- (Ce) the independent "group of oxalates " with the system no. IX / A.01 formed.

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 assigns zhemchuzhnikovite to the class of "organic compounds" and there to the department of "salts of organic acids". However, this section is further subdivided according to the type of salt-forming acid , so that the mineral can be found according to its composition in the sub-section "Oxalates", where it is the only member of the unnamed group 10.AB.35 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Zhemchuzhnikovit to the class of "organic minerals" and there in the department of the same name. Here he is with Stepanovit in the "Stepanovit group" with the system no. 50.01.07 within the sub-section " Salts of organic acids (oxalates) ".

Chemism

Mean values ​​from microprobe analyzes on zhemchuzhnikovite led to contents of 6.14% Al 2 O 3 , 5.95% Fe 2 O 3 , 0.06% MnO, 8.57% MgO, 5.69% Na 2 O, 0.12 % K 2 O, 42.88% C 2 O 3 , 29.09% H 2 O and 1.13% insoluble constituents (carbon), from which the empirical formula (Na 0.92 K 0.01 ) Σ = 0 93 Mg 1.06 (Al 0.60 Fe 3+ 0.37 ) Σ = 0.97 (C 2 O 4 ) 2.97 · 8.07H 2 O. It has been simplified to NaMg (Al, Fe 3+ ) (C 2 O 4 ) 3 · 8H 2 O and updated to NaMg (Fe 3+ 0.31 Al 0.69 ) (C 2 O 4 ) 3 · 9H 2 O .

The formula for synthesized zhemchuzhnikovite is given as NaMg (Fe 3+ 1 − x Al x ) (C 2 O 4 ) 3 · 9H 2 O. In synthetic crystals, the parameters for Fe 3+ and Al 3+ vary between 0.41: 0.59 and 0.76: 0.24 depending on the crystal. Each examined crystal shows its own statistical Fe 3+ / Al 3+ disorder, without which an order in a super cell would be recognizable. As a result, the structure of the zhemchuzhnikovite can have various Al / Fe compositions.

Zhemchuzhnikovit is the aluminum-dominant analogue of the Fe 3+ -dominated stepanovite, NaMgFe 3+ (C 2 O 4 ) 3 · 9H 2 O.

Crystal structure

Zhemchuzhnikovit crystallizes trigonal in the space group P 3 c 1 (space group no. 158) with the lattice parameters a  = 16.809  Å and c  = 12.658 Å as well as six formula units per unit cell . Template: room group / 158

Zhemchuzhnikovite has - like artificial MOF - a porous honeycomb-like structure with many cavities with Al 3+ and Fe 3+ disorder in the same position. As in Stepanovite, the cavities of each layer are occupied by Mg (H 2 O) 6 2+ , which are linked to the oxalate groups lining the pores via hydrogen bonds. The layers are connected to one another by hydrogen bonds to the water in the spaces between them. In each honeycomb layer of the Zhemchuzhnikovite all Fe 3+ ions have the same chirality (enantiomorphism), in contrast to Na + in the same layer. In contrast to Stepanovit, all layers in Zhemchuzhnikovit form ABABAB stacks, whereby all openings (apertures) of the honeycomb cavity are connected and form channels with a diameter of ≈ 0.9 nm. The arrangement of the hydrogen bonds around the water molecules in the interstices is similar to the situation in Stepanovit: each water molecule is a twofold donor compared to the oxalate ions in neighboring layers and a twofold acceptor compared to the guest molecule Mg (H 2 O) 6 2+ in the neighboring layers.

Artificially produced MOFs consist of open [M I M III (C 2 O 4 ) 3 ] 2− framework structures with a three- or two-dimensional network topology (honeycomb topology ), monovalent (M I ; e.g. Li + or Na + ) and trivalent (M III ; e.g. Cr 3+ or Fe 3+ ) cations as network nodes and divalent cations that are retained in the network cavities. Recently, similar metal oxalate structures based on zinc or other transition metals have become interesting as ferromagnetic and / or proton-conducting materials.

properties

morphology

Zhemchuzhnikovit forms needle-like to fibrous aggregates and very rarely also isometric to prismatic crystals about 0.05 mm in size, the main shape of which is the hexagonal prism II position {11 2 0}. The crystal costume is completed by the base pinacoid {0001} and the hexagonal dipyramid II position {22 4 1}.

physical and chemical properties

The crystals and aggregates of zhemchuzhnikovite are greenish-yellow to green and, especially in the case of synthetic crystals, have an alexandrite-like color effect with a smoke-green color in daylight and violet-amethyst-colored tones in artificial light. The line color is not specified, but the powder color of the green to yellow-green crystals should be a greenish white. The surfaces of the semi-transparent crystals show a clear glass-like sheen . Zhemchuzhnikovit has very low to low refraction and high birefringence.

The mineral shows good cleavability according to {0001}. There is no information on breakage and tenacity. Zhemchuzhnikovite has a Mohs hardness of 2 and is one of the soft minerals that, like the reference mineral plaster of paris, can be scratched with the fingernail. The measured density for zhemchuzhnikovit is 1.69 g / cm³, the calculated density is 1.66 g / cm³. Due to the variable chemical composition, the density also varies.

Zhemchuzhnikovit is easily soluble in water and can be recrystallized from solution. The pH of the solution is 5.51. Part of the water of crystallization is released at 85 ° C, the process being reversible at room temperature and in a water vapor-saturated atmosphere. After heating, initially a blackening occurs, then an infusible yellow-brown residue forms.

Education and Locations

As a very rare mineral formation, Zhemchuzhnikovit could only be described from one source so far (as of 2016). Its type locality is the "Chai-Tumus" (Tschaitumususk) brown coal deposit 200 km south of the Lena estuary in the former Okrug Bulunski , subject of the Republic of Sakha (Yakutia) , Far East Federal District in Siberia , Russia . The type material comes from a drill core from the permafrost zone at a depth of 230 m, which consisted of lignite saturated with ethanoic acid . Accompanying minerals are calcite , dolomite and stepanovite, other natural salts of organic acids such as. B. Oxalates (Whewellit, Weddellite and Glushinskit) as well as undefined acetates .

use

Due to its rarity, zhemchuzhnikovite has so far only been of interest to mineral collectors. Since the structures of Zhemchuzhnikovit (and Stepanovit) with their almost nanometer-wide openings and channels and their porous structure correspond to those of synthetically produced MOFs, it is now hoped to find more MOF-like crystals in nature that occur more frequently than the minerals investigated Zhemchuzhnikovit and Stepanovit and can therefore be used industrially. The organometallic framework structures (MOF) are coveted materials when it comes to storing and transporting gases (such as hydrogen and carbon dioxide ) as well as separating or catalyzing gaseous mixtures. MOFs can efficiently store and release hydrogen. They were also tested as filter material for the separation of carbon dioxide. Due to their porous structure with large surfaces of up to 4500 m² per gram, MOFs could also be of interest as efficient catalysts.

See also

literature

  • Zhemchuzhnikovit. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy. Mineralogical Society of America, 2001 ( PDF, 52 kB )
  • Juri N. Knipowitsch, AI Kombow, Evgeni Iwanowitsch Nefedow: On stepanovite and the new mineral zhemchuzhnikovite . In: Trudy. Vses. Nauchno-Issled. Geol. Inst. Band 96 , 1963, pp. 131-135 (Russian).
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th, revised and expanded edition. German publishing house for basic industry, Leipzig 1987, ISBN 3-342-00288-3 , p. 720 .

Web links

Individual evidence

  1. ^ A b c Karl F. Chudoba : Handbook of mineralogy by Carl Hintze . 1st edition. Supplementary volume III: New minerals and new mineral names (with supplements, corrections and additions) . Walter de Gruyter & Co., Berlin 1968, p.  289 ( books.google.de ).
  2. ↑ a b Hans Jürgen Rösler : Textbook of Mineralogy . 4th, revised and expanded edition. German publishing house for basic industry, Leipzig 1987, ISBN 3-342-00288-3 , p.  720 .
  3. ↑ a b c d e f g h i j k l m n o Igor Huskić, Igor V. Pekov, Sergey V. Krivovichev, Tomislav Friščić: Minerals with metal-organic framework structures . In: Science Advances . tape 2 , no. 8 , 2016, p. e1600621 , doi : 10.1126 / sciadv.1600621 ( advances.sciencemag.org [PDF; 793 kB ]).
  4. ^ 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.  719 .
  5. ↑ a b c d e f g Juri N. Knipowitsch, AI Kombow, Evgeni Iwanowitsch Nefedow: On stepanovite and the new mineral zhemchuzhnikovite . In: Trudy. Vses. Nauchno-Issled. Geol. Inst. (WSEGEI) . tape 96 , 1963, pp. 131-135 (Russian).
  6. ↑ a b c d e f g Zhemchuzhnikovit. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy. Mineralogical Society of America, 2001 ( PDF, 52 kB )
  7. ^ A b Igor V. Pekov: Minerals first discovered on the territory of the former Soviet Union . 1st edition. Ocean Pictures, Moscow 1998, ISBN 5-900395-16-2 , pp. 241 .
  8. ↑ Juri A. Shemtschushnikow, AI Ginsburg: Petrological foundations of the coals . 1st edition. Isd. Akad. Nauk SSSR, Moscow 1960, p. 93 (in Russian, published therein after a private communication from EI Nefedow).
  9. ↑ Mindat - Number of localities for Zhemchuzhnikovit
  10. ↑ Find location list for Zhemchuzhnikovit in the Mineralienatlas and in Mindat
  11. ^ A b Jan Oliver Löfken: "Natural metal-organic frameworks discovered". In: World of Physics. August 5, 2016. http://www.weltderphysik.de/gebiet/stoffe/news/2016/natuerliche-metallorganische-gerueste-entdeck/ (accessed on September 7, 2016).
  12. ↑ a b Manfred Lindinger: "Natural MOFs: Airy Crystals from the Heart of Nature". In: Frankfurter Allgemeine Zeitung. August 23, 2016. http://www.faz.net/aktuell/wissen/physik-mehr/luftige-kristalle-forschergruppe-entdeck-mofs-in-mineralien-14389805.html (accessed on September 7, 2016).