What is Niter?
Niter is potassium nitrate, a delicate evaporite mineral found as pale crusts and crystals in arid soils, caves and guano-rich deposits.
Mineralogy and crystal structure
Reference formula: KNO3. Niter is the low-temperature orthorhombic form of potassium nitrate. It is water-soluble and commonly occurs as efflorescent crusts, so preservation and humidity control are essential. Niter is classified with nitrates and has a orthorhombic crystal system. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 2.1–2.2.
Colour, lustre and habit
Typical colours include colourless, white, grey. The usual prismatic, acicular, crusty habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Niter forms in or is associated with arid soil crusts, cave deposits, guano accumulations and nitrate-rich fumarolic environments. Important documented localities include Chile, India, Egypt, South Africa, Spain and the United States.
A delicate evaporite from a dry landscape
Niter turns invisible soil chemistry into a pale crystal crust. Its solubility is part of the story and also the main reason a specimen needs careful storage.
Collecting and care
Keep dry and sealed from humidity; do not wash or expose to heat and handle nitrate-bearing material responsibly.
