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Doubly terminated blödite crystal from Soda Lake, San Luis Obispo County, California (size: 7.0 x 4.8 x 1.9 cm)
Category Sulfate minerals
(repeating unit)
Strunz classification 7.CC.50
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/a
Unit cell a = 11.04 Å, b = 8.15 Å,
c = 5.49 Å; β = 100.41°; Z = 2
Color Colorless, yellow, may be dark gray, bluish green, or reddish due to inclusions
Crystal habit Prismatic to equant crystals, granular, massive
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 2.5 - 3
Luster Vitreous
Specific gravity 2.23
Optical properties Biaxial (-)
Refractive index nα = 1.483, nβ = 1.486, nγ = 1.487
Birefringence δ = 0.004
2V angle 71° (measured)
References [1][2][3]

Blödite or bloedite is a hydrated sodium magnesium sulfate mineral with formula: Na2Mg(SO4)2·4H2O. The mineral is clear to yellow in color often darkened by inclusions and forms monoclinic crystals.

Blödite was first described in 1821 for an occurrence in a salt deposit in Ischler Salzberg, Bad Ischl, Gmunden, Austria and named for German mineralogist and chemist Karl August Blöde (1773–1820).[2][3]

It is found worldwide in evaporitic sedimentary environments such as the Great Salt Lake, Utah.

See also[edit]


Crystal from Soda Lake (size: 2.9 x 2.2 x 1.4 cm)