Kieserite

Kieserite
Kieserite
General
Category	Sulfate minerals
Formula (repeating unit)	MgSO4·H2O
Strunz classification	7.CB.05
Dana classification	29.6.2.1
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c
Unit cell	a = 7.51 Å, b = 7.61 Å c = 6.92 Å; β = 116.17°; Z = 4
Identification
Color	Colorless, grayish-white or yellowish
Crystal habit	Massive, granular; rarely as pyramidal crystals
Twinning	Contact on {001}, polysynthetic about [110]
Cleavage	{110} and {111} perfect
Fracture	Uneven
Tenacity	Fragile
Mohs scale hardness	3.5
Luster	Vitreous to dull
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.57
Optical properties	Biaxial (+)
Refractive index	nα = 1.520 nβ = 1.533 nγ = 1.584
Birefringence	δ = 0.064
2V angle	55°
Dispersion	r > v, moderate
Solubility	In water
References

Kieserite is the magnesium sulfate mineral (MgSO₄·H₂O) and is named after Dietrich Georg von Kieser (Jena, Germany 1862). It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic crystal system. Gunningite is the zinc member of the kieserite group of minerals.

Kieserite commonly occurs in marine evaporites and rarely in volcanic environments as a sublimate. It occurs in association with halite, carnallite, polyhalite, anhydrite, boracite, sulfoborite, leonite, epsomite and celestine.

In early 2005, Mars Express, a European Space Agency orbiter, discovered evidence of kieserite in patches of Valles Marineris (the largest canyon on Mars), along with gypsum and polyhydrated sulfates. This is direct evidence of Mars's watery past and augments similar discoveries made by the Mars Exploration Rover Opportunity in 2004.

It is used in the production of Epsom salt and as a fertilizer, the overall global annual usage in agriculture in the mid 1970s was 2.3 million tons.

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