Thenardite

  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 Thenard (1777-1826).

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Thenardite crystallizes in the orthorhombic system and often forms yellowish, reddish to grey white prismatic crystals although usually in massive crust deposits. It has a hardness of 2.5 - 3 and a specific gravity of 2.7. Thenardite is fluorescent, white in shortwave and yellow-green in longwave UV radiation.

Thenardite samples will gradually absorb water and convert to the mineral mirabilite, Na₂SO₄·10H₂O.

References

• Mineral galleries
• Webmineral
• Mindat