Nitratine

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. The typical form is as coatings of white, grey to yellowish brown masses. The rare crystals when found typically have the scalenohedral form of the calcite structure. It is found only as an efflorescence in very dry environments. It is very soluble in water such that it is deliquescent and will absorb water out of the air and turn into a puddle of sodium nitrate solution when exposed to humid air. There are nitratine deposits located in arid regions across the world such as in Chile, Mexico, Egypt, Peru, and South Africa. Chile is the only country to sell their deposits commercially as fertilizer.