Mendozite

Sulfate mineral
(repeating unit)NaAl(SO4)2·11H2OIMA symbolMz[1]Strunz classification7.CC.15Dana classification29.5.4.1Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupC2/cIdentificationFormula mass440.26 g/molColorcolorlessCrystal habitprismatic, pseudo-rhombohedralCleavage{100} good
{001} indistinct
{010} indistinctMohs scale hardness3LustervitreousStreakwhiteDiaphaneitytransparent to translucentDensity1.74 g/cm3Optical propertiesbiaxial (-)Refractive indexnα = 1.449
nβ = 1.461
nγ = 1.463Birefringenceδ = 0.0142V angle56° (measured)Solubilitysoluble in waterAlters totamarugiteReferences[2][3][4][5]

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.[3] It occurs in evaporites, presumably from the oxidation of sulfide minerals in the presence of clays.[3] 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).[4]

Bibliography

  • Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 469-471.

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ a b c Mendozite, WebMineral.com, retrieved 2009-11-28.
  4. ^ a b Mendozite, Mindat.org, retrieved 2009-11-28.
  5. ^ 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.


  • v
  • t
  • e