Starkeyite

Starkeyite
Mineralogical name	Starkeyite, Leonhardtite
Chemical name	Magnesiumsulfate Tetrahydrate
Trivial name
Chemical formula	MgSO4•4H2O
Other forms	Kieserite (MgSO4•H2O) Sanderite (MgSO4•2H2O) Pentahydrite (MgSO4•5H2O) Hexahydrite (MgSO4•6H2O) Epsomite (MgSO4•7H2O) Meridianite (MgSO4•11H2O) Magnesium 12-Hydrate
Crystal system	monoclinic
Crystal structure
Deliquescence humidity 20°C
Solubility (g/l) at 20°C
Density (g/cm³)	2.01 g/cm3
Molar volume	95.87 cm3/mol
Molar weight	192.43 g/mol
Transparency	translucent to opaque
Cleavage
Crystal habit
Twinning
Phase transition
Chemical behavior
Comments	unstable in air
Crystal Optics
Refractive Indices	nx = 1.49 ny = 1.491 nz = 1.497
Birefringence	Δ = 0.007
Optical Orientation	positive
Pleochroism
Dispersion	22°
Used Literature
{{{Literature}}}

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Literature

[Lide:1995]	Lide D.R. (eds.) Lide D.R. (1995): CRC Handbook of Chemistry and Physics, CRC Press
[Robson:1927]	Robson H.L. (1927): The System MgSO4-H2O from 68 to 240°. In: J. Amer. Chem. Soc., 49 (11), 2772-2783

[Robson:1927]

Robson H.L. (1927): The System MgSO4-H2O from 68 to 240°. In: J. Amer. Chem. Soc., 49 (11), 2772-2783

A phase is a physically distinctive form of matter and is characterized by having relatively uniform chemical and physical properties.