Mirabilite | |
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General | |
Category | Sulfate minerals |
Formula (repeating unit) |
Na2SO4·10H2O |
Strunz classification | 7.CD.10 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/c |
Identification | |
Formula mass | 322.9 g/mol |
Color | Colorless, white, yellowish-white, greenish-white |
Crystal habit | Granular or well-formed coarse crystals |
Twinning | Interpenetration twinning on {001}; also on {100} |
Cleavage | {100} perfect, {001} poor, {010} poor |
Fracture | Conchoidal |
Mohs scale hardness | 1.5–2 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent to translucent to opaque |
Specific gravity | 1.49 |
Optical properties | Biaxial (–), 2V=75.93° |
Refractive index | nα = 1.396, nβ = 1.4103, nγ = 1.419 |
Birefringence | δ = 0.023 |
Pleochroism | none |
Other characteristics | Not radioactive, non-fluorescent |
References |
Mirabilite, also known as Glauber's salt, is a hydrous sodium sulfate mineral with the chemical formula Na2SO4·10H2O. It is a vitreous, colorless to white monoclinic mineral that forms as an evaporite from sodium sulfate-bearing brines. It is found around saline springs and along saline playa lakes. Associated minerals include gypsum, halite, thenardite, trona, glauberite, and epsomite.
Mirabilite is unstable and quickly dehydrates in dry air, the prismatic crystals turning into a white powder, thenardite (Na2SO4). In turn, thenardite can also absorb water and converts to mirabilite.
Mirabilite is used as a purgative in the Traditional Chinese medicine; in Mandarin, it is called máng xiāo. Its name is based on the phrase "Sal mirabilis" (Latin for "wonderful salt") used by Johann Rudolph Glauber when he inadvertently synthesized mirabilite.