Zýkait
| Zýkait | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1976-039 |
| chemical formula | Fe 4 3+ [OH | SO 4 | (AsO 4 ) 3 ] · 15H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DB.45 ( 8th edition : VII / D.05) 05.33.03.02 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | Please complete |
| Lattice parameters | a = 20.85 Å ; b = 7.03 Å; c = 36.99 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | not defined (very soft) |
| Density (g / cm 3 ) | measured: 2.50; calculated: 2.504 |
| Cleavage | Please complete |
| Break ; Tenacity | uneven |
| colour | gray-white with a light yellowish-green or brownish tinge |
| Line color | light yellow |
| transparency | translucent |
| shine | Please complete |
| Crystal optics | |
| Refractive indices |
n α = 1.632 n β = 1.635 to 1.636 n γ = 1.646 |
| Birefringence | δ = 0.014 |
| Optical character | biaxial negative |
| Axis angle | 2V = 60 ° (measured); 56 to 66 ° (calculated) |
Zýkait is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition Fe 4 3+ [OH | SO 4 | (AsO 4 ) 3 ] · 15H 2 O, so it is chemically a water-containing iron arsenate with hydroxide and sulfate complex as additional anions .
Zýkait is translucent and only develops small, fine-needle crystals up to about 0.02 millimeters in length. It is usually found in the form of bulbous mineral aggregates up to about 3 centimeters in diameter or as massive cavity fillings. Zýkait is gray-white with a tinge of light yellowish-green or brownish.
Etymology and history
Zykaite was first discovered in the "Safary Mine" near Kaňk (Kutná Hora) in the Czech Republic and described in 1978 by F. Čech, J. Jansa, František Novák, who named the mineral after Václav Zýka (* 1926), the director of the Institute for Raw Materials in Kutná Hora.
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the zýkaite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where it belongs together with Bukovskýit , Diadochit , Pitticit and Sarmientit formed the unnamed group VII / D.05 .
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 zýkaite to the class of “phosphates, arsenates and vanadates” and there to the department of “phosphates etc. with additional anions ; with H 2 O “. However, this section is further subdivided according to the relative size of the cations involved and the molar ratio of the other anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4 <1: 1 “can be found where it is the only member of the unnamed group 8.DB.45 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns zýkaite to the class of "phosphates, arsenates and vanadates" and there in the department of "phosphates". Here he is together with Pitticit in the "Pitticit group" with the system no. 43.05.03 within the sub-section " Compound phosphates etc., (water-containing compound anions with hydroxyl or halogen) ".
Crystal structure
Zýkait crystallizes orthorhombically, although the exact space group has not yet been determined. The lattice parameters are a = 20.85 Å ; b = 7.03 Å and c = 36.99 Å and 8 formula units per unit cell .
Education and Locations
Zýkaite forms secondary as a weathering product from arsenopyrite and pyrite in the spoil heaps of old mines. In addition to arsenopyrite and pyrite, accompanying minerals include gypsum , kaňkite , limonite , pitticite, quartz and scorodite .
As a rare mineral formation, Zýkaite could only be detected at a few sites so far (as of 2012). In addition to its type locality “Safary Mine” near Kaňk, the mineral only appeared in the Czech Republic near Jáchymov (Sankt Joachimsthal).
In Germany, Zýkait was found in the pits “United Field”, “Reiche Zeche” and “Christbescherung” near Freiberg in the Saxon Ore Mountains and in Poland it has only appeared in the “Wilhelm Mine” near Stara Góra in the Bober-Katzbach Mountains (Lower Silesia ) come to light.
See also
literature
- F. Čech, J. Jansa, František Novák: Zýkaite, Fe 3+ 4 (AsO 4 ) 3 (SO 4 ) (OH) 15H 2 O, a new mineral . In: New yearbook for mineralogy, monthly books . 1978, p. 134-144 .
Web links
- Mineral Atlas: Zýkait (Wiki)
- Database-of-Raman-spectroscopy - Zýkaite (English)
- Webmineral - Zýkaite (English)
- RRUFF Database-of-Raman-spectroscopy - Zýkaite (English)
Individual evidence
- ↑ 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. 495 .
- ↑ a b Zýkaite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 64 kB ; accessed on November 13, 2018]).
- ↑ a b c Mindat - Zýkaite (English)