Thenardite
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| Thenardite | |
|---|---|
 Sodaville, Mineral County, Nevada | |
| General | |
| Category | Sulfate mineral |
| Formula (repeating unit) | Na2SO4 |
| Strunz classification | 07.AC.25 |
| Identification | |
| Formula mass | 142.04 |
| Color | White, grayish white, yellowish white, reddish white, brownish white |
| Crystal habit | Forms crust-like prismatic aggregates on matrix |
| Crystal system | Orthorhombic (2/m 2/m 2/m), Space group Fddd |
| Twinning | Interpenetration twinning on {001}; also on {100} |
| Cleavage | {010} Perfect |
| Fracture | Splintery |
| Mohs scale hardness | 2.5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 2.67–2.7, average = 2.68 |
| Optical properties | Biaxial (+), 2V=83° |
| Refractive index | nα = 1.471, nβ = 1.477, nγ = 1.484 |
| Birefringence | δ = 0.013 |
| Pleochroism | none |
| Other characteristics | Not radioactive, non-magnetic. Fluorescent and phosphorescent: short UV=bright white, long UV=bright white |
| References | [1][2] |
Thenardite is an anhydrous sodium sulfate mineral, Na2SO4 which occurs in arid evaporite environments. It also occurs in dry caves and old mine workings as an efflorescence and as a crusty deposit around fumaroles. It occurs in volcanic caves on Mt. Etna, Italy and was named after the French chemist, Louis Jacques Thénard (1777–1826).
Thenardite crystallizes in the orthorhombic system and often forms yellowish, reddish to grey white prismatic crystals although usually in massive crust deposits. Thenardite is fluorescent, white in shortwave and yellow-green in longwave UV radiation.
In humid conditions, thenardite gradually absorbs water and converts to the mineral mirabilite, Na2SO4·10H2O.
References
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