Halotrichite
| Halotrichite | |
|---|---|
 (size: 5.2 × 4.2 × 3.3 cm) |
|
| General and classification | |
| other names |
|
| chemical formula | Fe 2+ Al 2 [SO 4 ] 4 · 22 H 2 O |
|
Mineral class (and possibly department) |
Sulfates (and relatives) |
|
System no. to Strunz and to Dana |
7.CB.85 ( 8th edition : VI / C.12) 29.07.03.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | P 2 1 / a (No. 14) |
| Lattice parameters |
a = 21.26 Å ; b = 24.26 Å; c = 6.19 Å β = 100.3 ° |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 1.5 to 2 |
| Density (g / cm 3 ) | measured: 1.89; calculated: 1.95 |
| Cleavage | indistinct |
| Break ; Tenacity | shell-like |
| colour | white, gray, green |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.480 n β = 1.486 n γ = 1.490 |
| Birefringence | δ = 0.010 |
| Optical character | biaxial negative |
| Axis angle | 2V = 35 ° |
| Pleochroism | unavailable |
| Other properties | |
| Chemical behavior | water soluble; bitter, astringent taste |
Halotrichite , also known as mountain butter , iron alum , federalaun or salt or hair salt , is a rather seldom occurring mineral from the mineral class of " sulfates ( and relatives )".
Halotrichite crystallizes in the monoclinic crystal system with the chemical composition Fe 2+ Al 2 [SO 4 ] 4 · 22 H 2 O and develops mostly fibrous aggregates and crusty coatings, more rarely needle-shaped crystals of gray-white to apple-green color.
Etymology and history
Halotrichit was named after the Latin word halotrichum for hair salt , originally from ancient Gr . ἅλς háls “salt” and θριξ thríx , genitive τρίχος tríchos “hair”. The mineral was first found and described in 1839 by Ernst Friedrich Glocker .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the halotrichite belonged to the mineral class of "sulfates, selenates, tellurates, chromates, molybdates, tungstates" and there to the department of "hydrous sulfates without foreign anions ", where it belongs together with Apjohnit , Bílinit , Dietrichit , Pickeringit , Redingtonit and Wupatkiit formed a distinct group.
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), assigns halotrichite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and there into the department of " Sulphates (selenates etc.) without additional anions, with H 2 O “. However, this section is further subdivided according to the size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With only medium-sized cations”, where the “halotrichite group” with the system no. 7.CB.85 and the other members apjohnite, bilinite , caichengyunite , dietrichite, pickeringite, redingtonite and wupatkiite.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns halotrichite to the class of "sulfates, chromates and molybdates" and there to the category of "water-containing acids and sulfates". Here he is also the namesake of the "halotrichite group (monoclinic with 22 H 2 O)" with the system no. 07/29/03 and the other members apjohnite, bilinite, dietrichite, pickeringite, redingtonite and wupatkiite can be found within the subdivision of " water-containing acids and sulfates with A (B) 2 (XO 4 ) 4 × x (H 2 O) ".
Crystal structure
Halotrichite crystallizes monoclinically in the space group P 2 1 / a (space group no. 14) with the lattice parameters a = 21.26 Å ; b = 24.26 Å; c = 6.19 Å and β = 100.3 ° and 4 formula units per unit cell .
properties
Halotrichite is soluble in water. For this reason, crystals can flow apart in high humidity . Under dry conditions, the water of crystallization can be released , similar to other sulfates, whereby the mineral disintegrates.
Education and Locations
Halotrichite is normally secondary to oxidation from pyrite . But it is also found in solfataras and thermal springs . Accompanied will Halotrichit of various other sulfates.
As a rather rare mineral formation, halotrichite can sometimes be abundantly present at different sites, but overall it is not very common. So far (as of 2014) around 370 sites are known, including Catamarca , Salta and San Juan in Argentina ; in some regions of Australia ; Oruro and Potosí departments in Bolivia ; near Haskovo in Bulgaria ; in many regions of Germany ; Finland ; at the Solfatara of Pozzuoli in Italy ; Iran ; Nova Scotia , Québec and Yukon in Canada ; Chile ; People's Republic of China ; Carinthia , Salzburg and Styria in Austria ; as well as in many regions of Hungary and the USA .
See also
literature
- Ernst Friedrich Glocker: 18. Halotrichite, in outline of the mineralogy, including geognosy and petrefactology , published by Joh. Leonh. Schrag, Nuremberg 1839, pp. 691–691 (PDF 197.6 kB)
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 145 .
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 609 .
Web links
Individual evidence
- ↑ a b c d e f Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 386 .
- ↑ a b Halotrichite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 68.4 kB )
- ↑ a b c Mindat - Halotrichite (English)
- ↑ Mindat - Number of localities for halotrichite
- ↑ Find location list for halotrichite in the Mineralienatlas and Mindat