Potash is a collective term for a variety of potassium-bearing minerals, ores and refined products, all containing the element potassium in water-soluble form (minerals). The term potash comes from the Middle Dutch word potaschen (pot ashes, 1477). The old method of making potassium carbonate (K2CO3) was by collecting or producing wood ash (an occupation carried out by ash burners), leaching the ashes and then evaporating the resulting solution in large iron pots, leaving a white residue called pot ash. Approximately 10% by weight of common wood ash can be recovered as pot ash. Later, potash became the term widely applied to naturally occurring potassium salts and the commercial product derived from them.
Potash minerals were mined from at-surface and nearsurface Quaternary salt beds in the Dallol region of the Danakil Depression as long ago as the 14th Century. In the western world, the Germans were the first to discovery subsurface quantities of potash salts in the 1850s in the Zechstein Basin and a few years later had determined the utility of potash as a fertiliser for improving plant production. The first documented use of potash as a soil fertiliser in the USA was in 1873, and since the start of the 20th-century potash has been increasingly used to enhance agricultural productivity worldwide. Today, our ability to feed the world’s ever-expanding population is dependent on the use of various soluble potash salts as plant fertilisers (economics).
This change in potash usage from an ash product to an industrial chemical/fertiliser has changed the meaning of the term potash. Since the 1950s the terms, potash or potash salts, have been used commercially as general descriptions for potassium chloride (KCl or muriate of potash - MOP), potassium sulphate (K2SO4 or sulphate of potash - SOP), potassium-magnesium sulphate (K2SO4-MgSO4 or sulphate of potash magnesia), potassium nitrate (KNO3 or saltpetre), or mixed sodium-potassium nitrate (NaNO3 +KNO3 or Chilean saltpetre). Carnallite and sylvite are the most common naturally occurring potash mineral salts, with sylvite the most economically important. Other common potassium-entraining natural evaporite salts include: kainite, kieserite, langbeinite, leonite and polyhalite (minerals). Of these, carnallite, kainite, langbeinite and polyhalite when processed, can constitute potash ore minerals. Today, langbeinite ore is economically exploited only in New Mexico.