Mendozite
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| Mendozite | |
|---|---|
| General | |
| Category | Sulfate minerals, alum series |
| Chemical formula | NaAl(SO4)2·11H2O |
| Strunz classification | 07.CC.15 |
| Dana classification | 29.5.4.1 |
| Crystal symmetry | 2/m - Prismatic |
| Z | 4 |
| Identification | |
| Molar mass | 440.26 g/mol |
| Color | colorless |
| Crystal system | Monoclinic |
| Cleavage | {100} good {001} indistinct {010} indistinct |
| Mohs scale hardness | 3 |
| Luster | vitreous |
| Streak | white |
| Diaphaneity | transparent to translucent |
| Density | 1.74 g/cm3 |
| Refractive index | nα = 1.449 nβ = 1.461 nγ = 1.463 |
| Birefringence | δ = 0.014 |
| 2V angle | 56° (measured) |
| Solubility | soluble |
| Alters to | tamarugite |
| References | [1][2][3] |
Mendozite is a sulfate mineral, one of the alum series, with formula NaAl(SO4)2·11H2O. It is a hydrated form of sodium aluminium sulfate (soda alum).
It was discovered in western Argentina in 1868, probably near San Juan. The exact location has been lost, but was described as "San Juan, near Mendoza", and it is the latter city that give the mineral its name.[1] It occurs in evaporites, presumably from the oxidation of sulfide minerals in the presence of clays.[1] It is very soluble in water, and so can only be found in dry regions: however, in can still effloresce (lose water of crystallisation) in extremely arid climates, altering to tamarugite (the hexahydrate).[2]
References
- ↑ 1.0 1.1 1.2 Mendozite, <http://webmineral.com/data/Mendozite.shtml> (accessed 28 November 2009), WebMineral.com.
- ↑ 2.0 2.1 Mendozite, <http://www.mindat.org/show.php?id=2643> (accessed 28 November 2009), MinDat.org.
- ↑ Fang, J. H.; Robinson, P. D. Crystal structures and mineral chemistry of double-salt hydrates: II. The crystal structure of mendozite, NaAl(SO4)2·11H2O. American Mineralogist 1972, 57, 1081–88.
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