Thermonatrite

Thermonatrite is a naturally occurring evaporite mineral form of sodium carbonate, Na₂CO₃·H₂O.^[2][3]

Thermonatrite
Villiaumite and thermonatrite (powdery coating)
General
Category	Carbonate mineral
Formula	Na2CO3·H2O
IMA symbol	Tnat[1]
Strunz classification	5.CB.05
Crystal system	Orthorhombic
Crystal class	Pyramidal (mm2) H-M symbol: (mm2)
Space group	Pca21
Unit cell	a = 10.72 Å, b = 5.24 Å c = 6.46 Å; Z = 4
Identification
Colour	Colourless to grey or yellow, white
Crystal habit	Acicular crystals rare; typically occurs as powdery crusts
Cleavage	Poor to indistinct on {100}
Fracture	Sectile
Mohs scale hardness	1 – 1+1⁄2
Lustre	Vitreous
Diaphaneity	Transparent
Specific gravity	2.255 (measured on synthetic crystal)
Optical properties	Biaxial (−)
Refractive index	nα = 1.420 nβ = 1.506 nγ = 1.524
Birefringence	δ = 0.104
2V angle	48° (measured)
Solubility	Soluble in water
Other characteristics	Readily dehydrates
References	[2][3][4]

It was first described in 1845.^[4] Its name is from the Greek θερμός thermos, "heat", plus natron, because it may be a dehydration product of natron.^[3]

Typical occurrence is in dry saline lake beds and as soil encrustations. It has been reported from volcanic fumaroles and in association with carbonatite-related veins. Common associated minerals include trona, natron and halite.^[2]

See also

• Nahcolite
• Natron
• Niter
• Potassium nitrate
• Shortite
• Soda (disambiguation)
• Sodium sesquicarbonate
• Trona