Novgorodovait

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Novgorodovait
General and classification
other names

IMA 2000-039

chemical formula Ca 2 (C 2 O 4 ) Cl 2 • 2H 2 O
Mineral class
(and possibly department) 		Organic compounds
System no. to Strunz
and to Dana 		10.AB.80 ( 8th edition : IX / A.01)
50.01.10.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 6.936  Å ; b  = 7.382 Å; c  = 7.443 Å
β  = 94.3 °
Formula units Z  = 2
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) 2.38 (calculated); 2.40 (calculated)
Cleavage medium according to {100} and {010}
Break ; Tenacity fragile, brittle; uneven
colour colorless
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.565
n β  = 1.645
n γ  = 1.725
Birefringence δ = 0.16
Optical character biaxial negative
Axis angle 2V = 88 ° (measured), 86 ° (calculated)

Novgorodovaite is a very rarely occurring mineral from the mineral class of " organic compounds ". It crystallizes in the monoclinic crystal system with the chemical formula Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O, and is thus chemically seen a crystal water-containing calcium - oxalate - chloride .

Novgorodovaite of the type locality forms aggregates up to 3 cm in size from maximum 7 mm large grains. The mineral comes from the sylvinite potash deposit of the "Salt Dome Chelkar" in western Kazakhstan, where it was found together with anhydrite, gypsum, halite, bishopite, magnesite and hilgardite in drill cores that were obtained when drilling through evaporite rocks.

Etymology and history

In mineral samples in the Fersman Museum, which came from drill cores from the Chelkar salt dome at a depth of 850-900 m, a phase was identified that turned out to be a new mineral. It was recognized in 2000 after submission to the International Mineralogical Association (IMA) under the number IMA 2000-039 and in 2001 by a Russian research team with Nikita V. Chukanov , Dmitriy I. Belakovskii , Ramiza K. Rastsvetaeva , Oxana V. Karimova and Aleksandr E. Zadov described as novgorodovaite in the Russian science magazine "Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva" (Proceedings of the Russian Mineralogical Society).

The mineral was named after Margarita Ivanovna Novgorodova (* 1938), Russian mineralogist and director of the Fersman Museum of the Russian Academy of Sciences .

The type material for novgorodovaite is listed under catalog no. 69819 and 69820 in the collection of the Fersman Museum (Fersman Mineralogical Museum), Moscow , Russia .

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the novgorodovaite 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 , oxammite , stepanovite , Weddellite , wheatleyite , whewellite , zhemchuzhnikovite 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 novgorodovaite 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 in the sub-section "Oxalates" according to its composition, where it is the only member of the unnamed group 10.AB.80 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Novgorodovaite to the class of "organic minerals" and there in the department of the same name. Here he is the sole member of the unnamed group with the system no. 50.01.10 within the sub-section " Salts of organic acids (oxalates) ".

Chemism

Mean values ​​from microprobe analyzes on Novgorodovaite led to contents of 29.43% Ca; 24.56% Cl; 1.67% H; 8.53% C and (35.81)% O, giving the empirical formula Ca 2.00 (C 2 O 4 ) 0.97 Cl 1.89 (OH) 0.17 · 2.17H 2 O. It has been simplified to Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O, which is ideally 29.14% Ca; 8.73% C; 25.77% Cl; Requires 1.47% H and 34.89% O.

Crystal structure

Novgorodovaite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 6.936  Å ; b  = 7.382 Å; c  = 7.443 Å and β = 94.3 ° and two formula units per unit cell . Template: room group / 12

In the structure of novgorodovaite, the coordination environment of the calcium atom consists of an eight [vertex] polyhedron formed by the Cl atoms, the H 2 O molecules and the oxygen atoms of the C 2 O 4 groups . The CaX 8 polyhedra are linked to form wavy rows in the direction of the b-axis. In the two other directions, the polyhedra in the rows are linked by common edges (including the common H 2 O molecules and Cl atoms) to form a three-dimensional framework. The water molecules are involved in the weak symmetrical hydrogen bonds with the oxygen atoms of the oxalate anions.

Similar zigzag rows of eight-sided polyhedra have also been observed in the crystal structures of the two calcium oxalates whewellite and weddellite. This arrangement is responsible for the fact that the unit cell parameters in the direction of the chain axis have comparable values ​​in all three minerals. The replacement of one oxalate ion by two Cl atoms in the structure of the Novgorodovaite leads, however, to a deformation of the Ca polyhedron with considerably greater distances between Ca and Cl than between the other ligands. Furthermore, the three minerals differ in terms of the other parameters of the unit cell and in their symmetry.

In Novgorodovaite the centers of the oxalate ions are staggered in the (100) plane, whereas in Weddellite these ions lie parallel to each other in the same plane. In Whewellit, the oxalate ions are arranged alternately in relation to the y-axis (or z-axis), although they are also staggered. Therefore, in terms of its composition, the parameters of the unit cell, its symmetry and characteristic structural features, the novgorodovaite has no analogues among the other calcium oxalate minerals.

properties

morphology

Novgorodovait forms aggregates up to 3 cm in size from maximum 7 mm large grains. Idiomorphic crystals are not known.

physical and chemical properties

The crystal aggregates and grains of Novgorodovaite are colorless, but their streak color is always white. The surfaces of the transparent crystals show a clear glass-like sheen . Novgorodovaite has a medium to high light refraction and an extremely high birefringence (δ = 0.16) comparable to that of aragonite or calcite .

The mineral has two good (in the type publication “medium”) fissile properties according to {100} and {010}, but due to its brittleness and fragility it breaks similarly to amblygonite , with the fracture surfaces being uneven. Novgorodovaite has a Mohs hardness of 2.5 and is one of the soft minerals that are slightly easier to scratch with a copper coin than the reference mineral calcite . The measured density for novgorodovaite is 2.38 g / cm³, the calculated density is 2.40 g / cm³.

Education and Locations

Even if the novgorodovaite is the salt of an organic acid, anthropogenic or biogenic processes can be excluded during its formation. Novgorodovaite formed secondarily in marine evaporites , but the formation conditions of the mineral have not yet been clearly clarified. Begleitminerale of Novgorodovaits are anhydrite , gypsum , halite , Bischofite , magnesite and Hilgardit .

As a very rare mineral formation, Novgorodovaite could only be described from one source so far (as of 2016). Its type locality is the potash deposit of the "Salt Dome Chelkar" (Shalkar, Schalkar or Tschelkar, also Schalqar), which is located immediately south of the lake of the same name and approx. 100 km south-southeast of Oral , Terekti district , West Kazakhstan region in Kazakhstan . It is an area of ​​779 km² in the area of ​​the Caspian Depression , the center of which is approximately at these coordinates ( coordinates of the Chelkar Salt Dome ).

The salt dome, located approx. 160 km north of the sylvinite and borate deposit “Satimola”, contains sylvinite and bishofite carnallite horizons. It was discovered during hydrocarbon exploration in the early 1950s and has been studied since then. Since 2011 the "Chelkar" deposit has been intensively investigated with drilling campaigns and geophysically. Since the name "Chelkar" is a common term in Kazakhstan, it is often confused with other locations of this name. It should therefore be pointed out that the Chelkar potash salt deposit has nothing to do with the place Chelkar ( Schalqar ) in the Aqtöbe area , as it is sometimes stated.

use

Because of its rarity, novgorodovaite is only of interest to mineral collectors.

See also

literature

  • Nikita V. Chukanov, Dmitriy I. Belakovskii, Ramiza K. Rastsvetaeva, Oxana V. Karimova, Aleksandr E. Zadov: Novgorodovaite, Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O, a new mineral . In: Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva . 130 (Issue 4), 2001, p. 32-35 .
  • Ramiza K. Rastsvetaeva, Nikita V. Chukanov, Yurij V. Nekrasov: Crystal structure of novgorodovaite Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O (Translated from Doklady Akademii Nauk, Vol. 381, No. 3, 2001, pp. 353-355) . In: Doklady Chemistry . 381 (issue 3), 2001, p. 329-331 , doi : 10.1023 / A: 1012984825792 .

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k Nikita V. Chukanov, Dmitriy I. Belakovskii, Ramiza K. Rastsvetaeva, Oxana V. Karimova, Aleksandr E. Zadov: Novgorodovaite, Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O, a new mineral . In: Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva . 130 (Issue 4), 2001, p. 32-35 .
  2. ↑ Catalog of Type Mineral Specimens - N. (PDF 61 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  3. ↑ Ramiza K. Rastsvetaeva, Nikita V. Chukanov, Yurij V. Nekrasov: Crystal structure of novgorodovaite Ca 2 (C 2 O 4 ) Cl 2 · 2H 2 O (Translated from Doklady Akademii Nauk, Vol. 381, No. 3, 2001 , pp. 353-355) . In: Doklady Chemistry . 381 (issue 3), 2001, p. 329-331 , doi : 10.1023 / A: 1012984825792 .
  4. ^ Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 41 , 2003, p. 803–828 , doi : 10.2113 / gscanmin.41.3.803 ( rruff.info [PDF; 132 kB ]).
  5. ↑ Mindat - Number of localities for Novgorodovait
  6. ↑ Find location list for Novgorodovaite at the Mineralienatlas and at Mindat
  7. ↑ ERCOSPLAN: Independent Geological Report on the Zhilianskoe and Chelkar Potash deposits in Kazakhstan ESD 11-012 . ERcosplan Ingenieurgesellschaft Geotechnik und Bergbau mbH, Erfurt 2011, p. 1-74 ( kazakhpotash.com [PDF; 2.9 MB ]).
  8. ↑ Mindat - type locality for Novgorodovait
  9. ↑ Mineralienatlas - type locality for Novgorodovaite