Natron

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Natron
Natron deposits in the Era Kohor crater in the Tibesti Mountains, Chad
General
Category	Carbonate mineral
Formula (repeating unit)	Na2CO3·10H2O
IMA symbol	Nt[1]
Strunz classification	5.CB.10
Dana classification	15.01.02.01
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2/m
Unit cell	a = 12.75 Å, b = 9 Å, c = 12.6 Å β = 115.85°
Identification
Colour	Colourless to white, greyish, yellowish; colourless in transmitted light.
Crystal habit	crystalline, granular, and columnar crusts
Twinning	on {001}
Cleavage	On {001} distinct; on {010} imperfect; on {110} in traces.
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	1 – 1.5
Lustre	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	1.478
Optical properties	Biaxial (−)
Refractive index	nα = 1.405 nβ = 1.425 nγ = 1.440
Birefringence	δ = 0.035
2V angle	Measured: 71° , Calculated: 80°
Solubility	Soluble in water
References	[2][3][4]

Natron is a naturally occurring mixture of sodium carbonate decahydrate (Na₂CO₃·10H₂O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO₃) along with small quantities of sodium chloride and sodium sulfate. Natron is white to colourless when pure, varying to gray or yellow with impurities. Natron deposits are sometimes found in saline lake beds which arose in arid environments. Throughout history natron has had many practical applications that continue today in the wide range of modern uses of its constituent mineral components.

In modern mineralogy the term natron has come to mean only the sodium carbonate decahydrate (hydrated soda ash) that makes up most of the historical salt.