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Mendozite

Mendozite
Mendozite.jpg
General
CategorySulfate minerals, alum series
Formula
(repeating unit)
NaAl(SO4)2·11H2O
Strunz classification7.CC.15
Dana classification29.5.4.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Identification
Formula mass440.26 g/mol
Colorcolorless
Cleavage{100} good
{001} indistinct
{010} indistinct
Mohs scale hardness3
Lustervitreous
Streakwhite
Diaphaneitytransparent to translucent
Density1.74 g/cm3
Refractive indexnα = 1.449
nβ = 1.461
nγ = 1.463
Birefringenceδ = 0.014
2V angle56° (measured)
Solubilitysoluble
Alters totamarugite
References[1][2][3][4]

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.[2] It occurs in evaporites, presumably from the oxidation of sulfide minerals in the presence of clays.[2] 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).[3]

References

  1. ^ Mineralienatlas
  2. ^ a b c Mendozite, WebMineral.com, retrieved 2009-11-28.
  3. ^ a b Mendozite, MinDat.org, retrieved 2009-11-28.
  4. ^ Fang, J. H.; Robinson, P. D. (1972), "Crystal structures and mineral chemistry of double-salt hydrates: II. The crystal structure of mendozite, NaAl(SO4)2·11H2O", American Mineralogist, 57: 1081–88.