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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 07.CC.50
Crystal symmetry Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 21/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
Crystal system Monoclinic
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)