Thénardite

thenardite

aphthitalite

trona

tychite

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Formula: Na₂(SO₄)
Sulphate
Crystal System: Orthorhombic
Specific gravity: 2.664 measured, 2.674 calculated
Hardness: 2½ to 3
Streak: White
Colour: Colourless, light grey, light brown; colourless in transmitted light
Solubility: Soluble in water
Melting point: 883^oC
Environment:

Evaporite Deposits
Volcanic sublimates and fumeroles

Thénardite occurs in non-marine evaporite deposits in arid climates or it is formed by alteration of alkali-igneous rocks protected from water. It may deposit from volcanic gas at volcanic vents. In evaporite deposits it may be associated with trona and tychite, and in fumeroles with aphthitalite. In dry air mirabilite dehydrates to form thénardite, either as pseudomorphs of thénardite after mirabilite, or just crumbled to powder.

Localities

At Boron, Kramer district, Kern county, California, USA, thénardite pseudomorphs after mirabilite form as dehydration products (KL p187).

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