Thénardite

Thénardite is an anhydrous <a href="/facts/Sodium_sulfate/KWzpxTmj">sodium sulfate</a> mineral, Na2SO4 which occurs in arid <a href="/facts/Evaporite/vNW8fcEy">evaporite</a> environments, specifically <a href="/facts/Lake/YP0xxn0E">lakes</a> and <a href="/facts/Dry_lake/f2U3V1mP">playas</a>. It also occurs in dry <a href="/facts/Cave/SNfJTJtM">caves</a> and old <a href="/facts/Mining/g6uDIFab">mine</a> workings as an efflorescence and as a crusty <a href="/facts/Volcanic_sublimate/AA2lb6VE">sublimate</a> deposit around <a href="/facts/Fumarole/BX3XEkj5">fumaroles</a>. It occurs in <a href="/facts/Volcanic/c2M5upml">volcanic</a> caves on <a href="/facts/Mount_Etna/JygAnNnP">Mount Etna</a>, Italy. It was first described in 1825 for an occurrence in the Espartinas Saltworks in <a href="/facts/Ciempozuelos/JHhq9jL3">Ciempozuelos</a>, Spain, by the Spanish chemist José Luis Casaseca (1800 - 1869). Casaseca named the mineral after his master, the French chemist <a href="/facts/Louis_Jacques_Th%C3%A9nard/Le32ptEm">Louis Jacques Thénard</a> (1777–1857).
Thénardite crystallizes in the <a href="/facts/Orthorhombic/3zo4F8P0">orthorhombic</a> system and often forms yellowish, reddish to gray white prismatic crystals although usually in massive crust deposits. Thénardite is <a href="/facts/Fluorescent/qsJVT2qP">fluorescent</a>, white in shortwave and yellow-green in longwave <a href="/facts/Ultraviolet/kncBUqn5">UV</a> radiation. 
In humid conditions, thénardite progressively absorbs water and converts to the deca-hydrated mineral <a href="/facts/Mirabilite/LQpjYGMg">mirabilite</a>, Na2SO4 · 10 H2O.

Thénardite open-in-new

Thénardite