Pentahydrite
| Pentahydrite | |
|---|---|
| General and classification | |
| other names |
Epsom salt |
| chemical formula | Mg [SO 4 ] • 5H 2 O |
|
Mineral class (and possibly department) |
Water-containing sulfates without foreign anions |
|
System no. to Strunz and to Dana |
07.CB.20 ( 8th edition : VI / C.04) 06/29/07/03 |
| Similar minerals | Kieserite , hexahydrite , epsomite |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 |
| Lattice parameters |
a = 6.33 Å ; b = 10.55 Å; c = 6.07 Å α = 99.17 °; β = 109.88 °; γ = 75 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | 1.76 |
| Cleavage | Please complete |
| Break ; Tenacity | shell-shaped |
| colour | colorless, white, pale blue |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.482 n β = 1.492 n γ = 1.493 |
| Birefringence | δ = 0.011 |
| Optical character | biaxial negative |
| Other properties | |
| Chemical behavior | Easily soluble in water, bitter taste |
Pentahydrite (like epsomite also Epsom salt ; chemically magnesium sulfate pentahydrate ) is a rare mineral from the mineral class of " sulfates ( and relatives )". It crystallizes in the triclinic crystal system with the chemical composition Mg [SO 4 ] · 5H 2 O and usually develops granular aggregates and crusts of white color with a tinge of bluish. Colorless pentahydrite is also known. Like hexahydrite, larger crystals are rare.
Special properties
Like epsomite , pentahydrite is not stable. It can give off water in dry conditions. If the humidity is too high, pentahydrite crystals dissolve .
Etymology and history
Pentahydrite was first discovered in the area around Cripple Creek in the US state of Colorado and described in 1951 by Charles Palache, Harry Berman, Clifford Frondel, who derived the mineral based on its content of five molecules of crystal water after the Greek numeral πεντα penta for five and the Greek root ὕδωρ hyd (r) for water.
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the pentahydrite belonged to the mineral class of "sulfates, selenates, tellurates, chromates, molybdates, wolframates" and there to the department of "water-containing sulfates without foreign anions ", where they belong together with chalcanthite , Jôkokuit and Siderotil forms the so-called. Chalcanthitgruppe.
The 9th edition of Strunz's mineral systematics , valid since 2001 and used by the International Mineralogical Association (IMA), also assigns pentahydrite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and there in the department of "Sulphates (selenates etc.) without additional anions, with H 2 O".
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the pentahydrite to the class of "sulfates, chromates and molybdates", but there in the category of "hydrous acids and sulfates". Here is in the "Chalcanthite" with the system no. June 29, 2007 to be found in the subsection of " Water-containing acids and sulfates with AXO 4 × x (H 2 O) ".
Education and Locations
Due to the chemical relationship to the epsomite , the formation and the sites are comparable. Pentahydrite occurs as a secondary mineral as efflorescence on magnesium-containing rocks or minerals. Well-known sites are z. B. Grand Junction , Colorado / USA or Virginia City , Nevada / USA. Potential sources of pentahydrite are evaporites . Here it can crystallize out of oversaturated brine containing magnesium ( Basse-Casamance Valley / Senegal ). As with epsomite, pentahydrite can form in volcanic fumaroles . Pentahydrite occurs worldwide.
Other magnesium sulfates comparable to pentahydrite are kieserite , hexahydrite and epsomite . These are the respective mono-, hexa- or heptahydrates. These minerals can transform into one another through water absorption or water release. Occasionally, the corresponding metamorphoses are formed .
Crystal structure
Pentahydrite crystallizes triclinic-pinacoidal in the space group P 1 and the lattice parameters a = 6.33 Å, b = 10.55 Å, c = 6.07 Å, as well as α = 99.17 °, β = 109.88 °, γ = 75 °, as well as 2 formula units per unit cell .
use
Pentahydrite, like other water-soluble sulfates ( Mirabilit , Kieserit ), can be used as a laxative .
See also
Individual evidence
- ↑ a b Webmineral: Pentahydrite Mineral Data
- ↑ Mineral Atlas: Pentahydrite
- ^ Mindat: Pentahydrite mineral information and data.
- ↑ Webmineral: Pentahydrite Mineral Data
literature
- Charles Palache, Harry Berman, Clifford Frondel: 29.6.5.3 Pentahydrite [MgSO 4 · 5H 2 O] , in: The System of Mineralogy , Volume 2, 7th Edition, John Wiley and Sons, Inc New York, pp. 492-493 ( PDF 152.8 kB )
- Pentahydrite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.5 kB )