Görgeyit
| Görgeyit | |
|---|---|
 |
|
| General and classification | |
| other names |
Micheevit |
| chemical formula | K 2 Ca 5 [SO 4 ] 6 • H 2 O |
|
Mineral class (and possibly department) |
Sulfates (including selenates, tellurates, chromates, molybdates, and tungstates) |
|
System no. to Strunz and to Dana |
7.CD.30 ( 8th edition : VI / C.20) 04/29/07/01 |
| Crystallographic Data | |
| Crystal system | prismatic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | C 2 / c (No. 15) |
| Lattice parameters |
a = 17.51 Å ; b = 6.82 Å; c = 18.21 Å β = 113.3 ° |
| Formula units | Z = 4 |
| Frequent crystal faces | {001}, {100}, {111}, {110} |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | measured: 2.90 to 2.93; calculated: 2.90 |
| Cleavage | imperfect after {100} |
| Break ; Tenacity | splintery to hooky |
| colour | colorless, white, light yellow, greenish yellow |
| Line color | White |
| transparency | translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.560 n β = 1.569 n γ = 1.584 |
| Birefringence | δ = 0.024 |
| Optical character | biaxial positive |
| Axis angle | 2V = 79 ° (measured); 78 ° (calculated) |
Görgeyite is a very rarely occurring mineral from the mineral class of "sulfates (including selenates, tellurates, chromates, molybdates and wolframates)". It crystallizes in the monoclinic crystal system with the chemical composition K 2 Ca 5 [SO 4 ] 6 · H 2 O and is therefore chemically a water-containing potassium - calcium - sulfate .
Görgeyit usually develops tabular crystals with a glass-like sheen on the surfaces. In its pure form, Görgeyite is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or polycrystalline formation, it can also appear white and, due to foreign admixtures, take on a light yellow or greenish yellow color, the transparency decreasing accordingly.
With a Mohs hardness of 3.5 to 4, Görgeyite is one of the medium-hard minerals that, like the reference mineral fluorite, can be easily scratched with a pocket knife .
Special properties
Görgeyit dissolves poorly in boiling water, which means that it loses little or no weight, but the crystal surfaces become rough .
Etymology and history
Görgeyite was first discovered in the "Leopold Horizont" of the Bad Ischl salt mine in Upper Austria and described in 1953 by Heimo Mayrhofer , who named the mineral after the Austrian mineralogist Rudolf von Görgey ( Rudolf Görgey von Görgö and Toporcz , 1886–1915).
A mineral described by EI Nefedov in 1954 and called Mikheevite turned out to be identical to Görgeyite despite minor differences in composition and crystal system.
Type material of the mineral is kept in the Natural History Museum Vienna (catalog no. M474) in Austria and at Harvard University (catalog no. 107559) in Cambridge, Massachusetts in the USA.
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Görgeyite belonged to the mineral class of "sulfates, chromates, molybdates, wolframates" (including some selenates and tellurates) and there to the department of "water-containing sulfates, without foreign anions " , where together with Leightonit and Polyhalit he created the "Polyhalit Group" with the system no. VI / C.20 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 Görgeyit in the category of "sulfates (selenates, etc.) without additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the subsection “With only large cations”, where it is the only member of the unnamed group 7.CD.30 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Görgeyit to the class of "sulfates, chromates and molybdates" and there in the category of "water-containing acids and sulfates". Here he is to be found as the only member of the unnamed group 04/29/07 within the sub-section “Hydrous acids and sulphates with (A + ) 2 B n (XO 4 ) p × x (H 2 O)”.
Education and Locations
Görgeyit formed secondarily in evaporite - deposits and in hydrothermal - veins . Accordingly, the mineral can predominantly be associated with other evaporite minerals such as anhydrite , gypsum , glauberite , halite and polyhalite , but also with cesanite and / or pyrite .
In addition to its type locality Bad Ischler Salzberg, which is also the only known site in Austria to date, the mineral has so far (as of 2014) only been discovered at five other sites. The boron deposit "Inder B" (also Inder See or Inder Salt Dome) near Atyrau in Kazakhstan with crystal finds of up to eight centimeters in length became particularly well known .
The only known site in Germany so far is the Anna mine near Alsdorf in North Rhine-Westphalia.
Görgeyit was also found in the Cesano geothermal area near Lake Bracciano in the Italian region of Latium and in the Jianghan (Wuhan) and Qu (Dazhou) salt deposits in China.
Crystal structure
Görgeyite crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a = 17.51 Å ; b = 6.82 Å; c = 18.21 Å and β = 113.3 ° as well as 4 formula units per unit cell .
See also
literature
- Heimo Hayrhofer: Görgeyite, a new mineral from the Ischl salt deposit. In: New Yearbook for Mineralogy. MONTHS, 1953, pp. 35–44
- Michael Fleischer : New mineral names. In: American Mineralogist. Volume 39 (1954), pp. 402-408 ( PDF 383.2 kB ; Görgeyit p. 2)
Web links
- Mineral Atlas: Görgeyit (Wiki)
- Web mineral - Görgeyite
- Database-of-Raman-spectroscopy - Görgeyite
- American-Mineralogist-Crystal-Structure-Database - Görgeyite
- austria-forum.org - Görgeyit
Individual evidence
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 669 .
- ↑ a b c d e 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. 392 .
- ↑ a b c Görgeyite , 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 )
- ↑ a b c Mindat - Görgeyite
- ↑ Michael Fleischer : New mineral names. In: American Mineralogist. Volume 39 (1954), pp. 402-408 ( PDF 383.2 kB ; Görgeyit p. 2)
- ^ Margret Hamilton, Franz Pertlik: Rudolf GÖRGEY VON GÖRGÖ AND TOPORCZ (1886 - 1915). A pioneer in the exploration of central European salt deposits. In: Reports of the Federal Geological Institute. , ISSN 1017-8880 , Vienna 2013, p. 101 ( PDF 351.5 kB )
- ↑ Michael Fleischer: New mineral names. In: American Mineralogist. Volume 40 (1955), pp. 551–554 ( PDF 236.7 kB )
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 ( Dörfler Natur ).
- ↑ Find location list for Görgeyit at the Mineralienatlas and at Mindat