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 index are nω = 1.587 and nε = 1.336.Nesse, W, introduction to Optical Mineralogy, Fourth Edition (Oxford, New York, Oxford University Press) 2013. appendix II, B.3
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. The salt bed that is mined contains more minerals than just nitratine often containing sulfurous minerals as well as Iodine. Around 600,000 tons of nitratine are mined in Chile each year with other products such as Iodine and sodium sulfate mined as well.
Nitratine happens to be isostructural to calcite, CaCO3, a widespread naturally occurring mineral, although nitratine dissolution and crystallization occur much faster than the same processes for calcite. The structural similarity makes nitratine a very useful mineral for laboratory experiments concerning pressure dissolution and other experiments such as serving as a proxy for the deformation and formation of calcite.
The Saltpeter War (1480–1510)Enciclopedia de Mexico, 2005, , p.1542 and the War of the Pacific (1879–1884)
The mineral also has a wide range of applications beyond being used as a fertilizer in agricultural practices. Nitratine has been used in the Explosive industry for water-containing slurry as well as gel explosives. It is also used as a refining agent to remove air bubbles by the glass and enamel industries. Nitratine, other alkali nitrates, or nitrites also have applications for solar technology serving as a heat-transfer or heat-storage medium. Nitratine can also be used as a substitute for potassium nitrate in gunpowder.
|
|