Nitratine

Nitratine or nitratite, also known as cubic niter (UK: nitre), soda niter or Chile saltpeter (UK: Chile saltpetre), is a <a href="/facts/Mineral/LkUFbNmv">mineral</a>, the naturally occurring form of <a href="/facts/Sodium_nitrate/8WteItRf">sodium nitrate</a>, NaNO3. Chemically it is the sodium analogue of <a href="/facts/Saltpeter/vVeaDn51">saltpeter</a>. Nitratine crystallizes in the <a href="/facts/Rhombohedral_crystal_system/sSSok8wo">trigonal</a> system, but rarely occurs as well-formed crystals. It is isostructural with <a href="/facts/Calcite/gKMHYQJo">calcite</a>. It is relatively soft and light with a <a href="/facts/Mohs_hardness/wXBMcVIm">Mohs hardness</a> of 1.5 to 2 and a <a href="/facts/Specific_gravity/ySquGd2x">specific gravity</a> of 2.24 to 2.29. Its <a href="/facts/Refractive_index/yjkzvgeE">refractive indices</a> 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 <a href="/facts/Calcite/gKMHYQJo">calcite</a> structure. It is found only as an <a href="/facts/Efflorescence/MVErNa6p">efflorescence</a> in very dry environments. It is very soluble in water such that it is <a href="/facts/Deliquescent/1NBGewXv">deliquescent</a> 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 <a href="/facts/Crystallization/oCUUG80k">crystallization</a> 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 <a href="/facts/Saltpeter_War_(Mexico)/Jyv8KTMu">Saltpeter War</a> (1480–1510) and the <a href="/facts/War_of_the_Pacific/MgdGmxSo">War of the Pacific</a> (1879–1884) were fought over the control of saltpeter deposits.

Nitratine open-in-new

Nitratine