| Niter | |
|---|---|
| General | |
| Category | Nitrate minerals |
| Chemical formula | KNO3 |
| Strunz classification | 05.NA.10 |
| Dana classification | 18.1.2.1 |
| Crystal symmetry | 2/m 2/m 2/m |
| Identification | |
| Color | white |
| Crystal habit | encrustations |
| Crystal system | orthorhombic |
| Cleavage | very good on {001}; good on {010} |
| Fracture | brittle |
| Mohs scale hardness | 2 |
| Luster | vitreous |
| Streak | white |
| Diaphaneity | transparent |
| Specific gravity | 2.10 (calc.) |
| Refractive index | nα = 1.332 nβ = 1.504 nγ = 1.504 |
| Solubility | soluble |
| References | [1][2][3] |
Niter (US) or nitre (UK) is the mineral form of potassium nitrate, KNO3, also known as saltpeter (US) or saltpetre (UK). Historically, the term "nitre" – cognate with "natrium", a Latin word for sodium – has been very vaguely defined, and it has been applied to a variety of other minerals and chemical compounds, including sodium nitrate (also "soda nitre" or "cubic nitre"), sodium carbonate and potassium carbonate. This article is about the mineral form of potassium nitrate, which is the usual modern meaning.
Because of its ready solubility in water, niter is most often found in arid environments. A major source is the Atacama desert in Chile. Potassium and other nitrates are of great importance for use in fertilisers, and, historically, gunpowder. Much of the world's demand is now met by synthetically produced nitrates, though the natural mineral is still mined and is still of significant commercial value: as of 2007, Chilean potassium nitrate was reportedly trading at around USD 1000 per tonne.[4]
Contents |
Niter is a colourless to white mineral crystallizing in the orthorhombic crystal system. It usually is found as massive encrustations and effervescent growths on cavern walls and ceilings where solutions containing alkali potassium and nitrate seep into the openings. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show twinning.
Niter has been known since ancient times. The name is from Hebrew néter, for salt-derived ashes. It may have been used as, or in conjunction with soap, as implied by Jeremiah 2:22, "For though thou wash me with nitre, and take thee much sope…" However, it is not certain which substance (or substances) the Biblical "neter" refers to, with some suggesting sodium carbonate. A term (ἀφρόνιτρον) which translates as "foam of nitre" was a regular purchase in a fourth-century AD series of financial accounts, and since it was expressed as being "for the baths" was probably used as soap.[5]
In literature, Edgar Allan Poe invokes the use of nitre in the short story "The Cask of Amontillado" (1846), in which the main character, Montresor, describes the mineral deposits lining the walls of the underground catacombs, where he lures Fortunato to his death.
   | Niter page on mindat.org - Niter: Niter mineral information and data. |
| | Niter page on webmineral.com - Niter Mineral Data |
| | Mineral galleries - NITER (Potassium Nitrate) |
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