Dashkovait

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Dashkovait
General and classification
other names

IMA 2000-006

chemical formula Mg (HCOO) 2
Mineral class
(and possibly department) 		Organic Compounds - salts of organic compounds
System no. to Strunz
and to Dana 		10.AA.10 ( 8th edition : IX / A.02)
0250-06-02
Similar minerals Formicaite
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 8.69  Å ; b  = 7.18 Å; c  = 9.39 Å
β  = 97.6 °
Formula units Z  = 4
Physical Properties
Mohs hardness 1
Density (g / cm 3 ) 1.75
Cleavage Please complete!
Break ; Tenacity uneven
colour White
Line color White
transparency semi-transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.465
n β  = 1.486
n γ  = 1.516
Birefringence δ = 0.051
Optical character biaxial (+)
Other properties
Chemical behavior easily soluble in water

Dashkovaite is an extremely rare mineral from the mineral class of " organic compounds ". It crystallizes in the monoclinic crystal system with the chemical composition Mg (HCOO) 2 , so from a chemical point of view it is a magnesium formate .

Dashkovaite rarely develops well-defined, tabular crystals . Mostly it forms small, spherical, porous or fibrous mineral aggregates . The largest crystals found so far were about 3 mm in size. The mineral is comparatively soft ( Mohs hardness 1).

Etymology and history

The name of the mineral goes back to the Russian princess and scholar Ekaterina Romanovna Voronzowa-Daschkowa (1743–1810), who was the first woman to head the Russian Academy of Sciences as director. Dashkovait was recognized as a mineral by the International Mineralogical Association (IMA) in 2000 .

After Formicaite , Dashkovaite is the second formate to be officially recognized as a mineral by the IMA.

classification

In the outdated, but still in use 8th edition of the mineral classification according to Strunz , the dashkovaite belonged to the mineral class of "organic compounds" and there to the department of "salts of organic acids", where it belongs together with abelsonite , calclacite , earlandite , formicaite, hoganite , julienite , Kafehydrocyanit , Mellit and Paceit the "Mellit-Julienit-Gruppe" with the system no. IX / A.02 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 classifies the Dashkovait in the "Salts of organic acids" section. However, this is further subdivided according to the salt-forming acid, so that the mineral can be found according to its composition in the sub-section "Acetate", where it is the only member of the unnamed group 10.AA.10 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Dashkovait to the class and department of the same name of "organic minerals". Here it is together with Formicait in the "Formicait series" with the system no. 50.02.06 within the sub-section of " Salts of organic acids (mellitates, citrates, cyanates and acetates) ".

Crystal structure

Dashkovaite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 8.69  Å , b  = 7.18 Å, c  = 9.39 Å and β = 97.6 ° and 4 Formula units per unit cell . Template: room group / 14

properties

Like formicait , dashkovait is easily soluble in water and therefore not stable. The hygroscopic crystals in the air at high humidity to dissolve .

From a chemical point of view, dashkovait is the magnesium salt of formic acid , with the chemical formula Mg (HCOO) 2 . Even if Dashkovait is the salt of an organic acid, its formation is not necessarily linked to biological organisms. Magnesium formate can be formed by purely inorganic compounds (see the comparable illustration of calcium formate ).

Education and Locations

Dashkovait has so far only been detected in one iron deposit in a skarn . In addition to iron and boron minerals, it was found in a salty rock. Associated minerals are: Shabynite , Iowaite , Ekaterinite , Korshunovskite , Halite, and Hydromagnesite .

So far (as of 2013) only two sites in Russia have become known:

See also

literature

Web links

Individual evidence

  1. ↑ Dashkovaite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.5 kB )
  2. ↑ a b K. Osaki, Y. Nakai, T. Watanabe: The crystal structure of magnesium formats dihydrate and manganous formats dihydrate Locality: synthetic In: Journal of the Physical Society of Japan Volume 19 (1964), pp. 717–723 ( Crystal data available online at crystallography.net )
  3. ↑ List of localities for Dashkovaite in the Mineralienatlas and Mindat