nitratine

{{Infobox mineral | name = Nitratine | boxwidth = | boxbgcolor = | image = Nitratine-548175.jpg | imagesize = 260px | alt = | caption = | category = Nitrate minerals | formula = NaNO3 | IMAsymbol = Ntt | molweight = 84.99 g/mol | strunz = 5.NA.05 (10th edition) 5/A.01-10 (8th edition) | system = Trigonal | class = Hexagonal scalenohedral (m) H-M symbol: ( 2/m) | symmetry = Rc (no. 167) | unit cell = a = 5.06 Å, c = 16.82 Å; Z = 6 | color = Colorless, white, gray, yellowish, brownish | habit = Granular – Generally occurs as anhedral to subhedral crystals in matrix; massive – Uniformly indistinguishable crystals forming large masses | cleavage = {1011} Perfect | fracture = | tenacity = Sectile – curved shavings or scrapings produced by a knife blade | mohs = 1.5 – 2 | luster = Vitreous (glassy) | refractive = nω = 1.580 – 1.587 nε = 1.330 – 1.336 | opticalprop = Uniaxial (−) | birefringence = δ = 0.250–0.251 | pleochroism = | streak = White | gravity = 2.26 | density = | melt = | fusibility = | diagnostic = | solubility = Readily soluble in water | diaphaneity = Transparent | other = Slightly deliquescent | references = }}

Nitratine or nitratite, also known as cubic niter (UK: nitre), soda niter or Chile saltpeter (UK: Chile saltpetre), is a mineral, the naturally occurring form of sodium nitrate, NaNO3. Chemically it is the sodium analogue of saltpeter. Nitratine crystallizes in the trigonal system, but rarely occurs as well-formed crystals. It is isostructural with calcite. It is relatively soft and light with a Mohs hardness of 1.5 to 2 and a specific gravity of 2.24 to 2.29. Its refractive indices are nω = 1.587 and nε = 1.336.