Glauberite
(repeating unit)Na2Ca(SO4)2 IMA symbol Glb[1] Strunz classification 7.AD.25 Crystal system Monoclinic Crystal class Prismatic (2/m)
(same H-M symbol) Space group C2/c Unit cell a = 10.129, b = 8.306
c = 8.533 [Å]; β = 112.19°; Z = 4 Identification Color Gray or pale yellow, colorless Crystal habit Tabular prismatic crystals Cleavage Perfect on {001}, imperfect on {110} Fracture Conchoidal Tenacity Brittle Mohs scale hardness 2.5–3 Luster Vitreous to waxy, pearly on cleavages Streak White Diaphaneity Transparent to translucent Specific gravity 2.75–2.85 Optical properties Biaxial (−) Refractive index nα = 1.507 – 1.515 nβ = 1.527 – 1.535 nγ = 1.529 – 1.536 Birefringence δ = 0.022 2V angle 24° to 34° Dispersion strong r > v Solubility HCl and H2O (water) soluble Alters to readily alters to gypsum Other characteristics often a pseudomorph References [2][3][4] 
(same H-M symbol)
c = 8.533 [Å]; β = 112.19°; Z = 4
Glauberite is a monoclinic sodium calcium sulfate mineral with the formula Na2Ca(SO4)2.
It was first described in 1808 for material from the El Castellar Mine, Villarrubia de Santiago, Toledo, Castile-La Mancha, Spain. It was named for the extracted Glauber's salts after the German alchemist Johann Rudolf Glauber (1604–1668).[2]
Glauberite often forms in continental and marine evaporite deposits, but may also form from hydrothermal deposits, as mineral sublimates deposited near fumaroles, in amygdules in basalt, and in nitrate deposits in arid climates. It occurs associated with halite, polyhalite, anhydrite, gypsum, thenardite, mirabilite, sassolite and blodite.[4]
Because of its solubility, glauberite is often dissolved away from the crystal matrix leaving a distinctly shaped hollow cast. Its mineral composition is readily altered into other minerals as pseudomorphs. Gypsum pseudomorphs are common due to increased humidity.
Glauberite, its cast impressions, and its pseudomorphed crystals are often easily recognizable due to its common crystal twinning, and crystal habit displayed by uniquely shaped flattened, often seeming rhombohedral, large individual 'floater crystals'.
The mineral is commercially mined for its sulfate contents.[5]
References
- ^ 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.
- ^ a b Glauberite on Mindat
- ^ Glauberite data on Webmineral
- ^ a b Glauberite in the Handbook of Mineralogy
- ^ Chen, Shuzhao; Zhang, Donghua; Shang, Tao; Meng, Tao (August 2018). "Experimental Study of the Microstructural Evolution of Glauberite and Its Weakening Mechanism under the Effect of Thermal-Hydrological-Chemical Coupling". Processes. 6 (8): 99. doi:10.3390/pr6080099.
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