Tachyhydrite
| Tachyhydrite | |
|---|---|
| General and classification | |
| other names |
Tachhydrite |
| chemical formula |
|
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.BB.35 ( 8th edition : III / C.08) 05/11/05/01 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | trigonal-rhombohedral; 3 |
| Room group (no.) | R 3 (No. 148) |
| Lattice parameters | a = 10.14 Å ; c = 17.32 Å |
| Formula units | Z = 3 |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 1.667; calculated: 1.673 |
| Cleavage | completely according to {10 1 1} |
| colour | colorless, waxy to honey yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.520 n ε = 1.512 |
| Birefringence | δ = 0.008 |
| Optical character | uniaxial negative |
| Other properties | |
| Chemical behavior | very easily soluble in water, very hygroscopic (water-absorbent) |
| Special features | sharp, bitter taste |
Tachyhydrite (also tachhydrite ) is a rarely occurring mineral from the mineral class of " halides ". It crystallizes in the trigonal crystal system with the composition CaMg 2 Cl 6 · 12H 2 O, so from a chemical point of view it is a water-containing calcium - magnesium - chloride .
Tachyhydrite is transparent to translucent and usually develops round, colorless or waxy to honey-yellow masses. When drawn synthetically , the mineral also forms rhombohedral or tabular crystals .
With a Mohs hardness of 2, tachyhydrite is one of the soft minerals and, like the reference mineral plaster, can be scratched with the fingernail.
Special properties
The mineral is very soluble in water. One liter of water with a temperature of 18.75 ° C can absorb 1603 grams of tachyhydrite.
Etymology and history
Tachyhydrite owes its name to its hygroscopic property of extracting moisture from the ambient air and then quickly dissolving it . The name was derived from the ancient Greek words ταχύς [tachýs] for fast and ὕδωρ [hydor] for water , which means “fast water”.
The mineral was first discovered in the rock salt - deposits at Stassfurt in Saxony-Anhalt and described in 1856 by Karl Friedrich Rammelsberg .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the tachyhydrite belonged to the division of "double halides (mostly with OH, H 2 O)", where together with carnallite it forms the "carnallite-tachyhydrite group" with the system -No. III / C.08 and the other members Koenenit and Redikortsevit .
In contrast , the 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies tachyhydrite under the category of "Simple halides with H 2 O". This is further subdivided according to the molar ratio of metal (M) to the respective halogen (X), so that the mineral can be found according to its composition in the sub-section "M: X = 1: 2", where it is the only member of the unnamed Group 3.BB.35 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns tachyhydrite to the class of "halides", but there it belongs to the department of "complex halides - aluminum fluorides". Here he is to be found as the only member of the unnamed group 11.05.05 within the subdivision of " Complex halides - aluminum fluorides with (A) m B (X) 6 ".
Education and Locations
Tachyhydrite separates from residual liquors with a high magnesium content in marine salt deposits . As Begleitminerale occur among others anhydrite , Bischofite , carnallite , halite , kainite , kieserite and sylvite on.
As a rare mineral formation, tachyhydrite could so far (as of 2012) only be detected at a few sites, with a little more than 10 sites being known. In addition to its type locality in Staßfurt, the mineral was also found in Germany at Tarthun and in the Krügershall Teutschenthal potash works in Saxony-Anhalt, as well as in several potash mines near Celle , Reyershausen (Königshall-Hindenburg potash plant), Frenswegen , Peine (Desdemona potash plant) and in the Vienenburg potash plant .
The only Austrian site to date is the rock salt deposit near Dürrnberg in Salzburg.
Furthermore, tachyhydrite was found in the Mengo mine field in the Kouilou department of the Republic of Congo, in the Billingham anhydrite mine and in the Carlsbad potash plant in Eddy County of the US state New Mexico.
Crystal structure
Tachyhydrite crystallizes trigonal in the space group R 3 (space group no. 148) with the lattice parameters a = 10.14 Å and c = 17.32 Å as well as 3 formula units per unit cell .
use
One patent describes how tachyhydrite is formed by treating carbonates containing magnesium with strong hydrochloric acid. This can become an obstacle to oil production if it closes pores.
literature
- CF Rammelsberg: About the tachyhydrite, a new mineral from the rock salt deposit of Stassfurth , in: Poggendorffs Annalen der Physik und Chemie , Volume 98 (1856), pp. 261–263 ( PDF 294.5 kB )
- Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 336 .
Web links
- Mineral Atlas: Tachyhydrite
- Thomas Witzke (Stollen Troll): The discovery of tachyhydrite
- Web mineral - tachyhydrite
Individual evidence
- ↑ 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. 158 .
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 366, 841 .
- ↑ a b c Tachyhydrite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 67.9 kB )
- ↑ a b c Mindat - Tachyhydrite
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 336 .
- ↑ Mindat - Number of localities for tachyhydrtite
- ^ John A. Knox: Utilization of high strength acid on dolomite . 1969.