natron

{{Infobox mineral | name = Natron | category = Carbonate mineral | boxwidth = | boxbgcolor = | image = Emi Koussi crater natron.jpg | imagesize = | alt = | caption = Natron deposits in the Era Kohor crater in the Tibesti Mountains, Chad | formula = Na2CO3·10H2O | IMAsymbol = Nt | molweight = | strunz = 5.CB.10 | dana = 15.01.02.01 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P2/m | unit cell = a = 12.75 Å, b = 9 Å, c = 12.6 Åβ = 115.85° | colour = Colourless to white, greyish, yellowish; colourless in transmitted light. | 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 = 1 – 1.5 | lustre = Vitreous | streak = White | diaphaneity = Transparent to translucent | gravity = 1.478 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.405 nβ = 1.425 nγ = 1.440 | birefringence = δ = 0.035 | pleochroism = | 2V = Measured: 71° , Calculated: 80° | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = Soluble in water | other = | alteration = | references = }} 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.