Salammoniac, also sal ammoniac or salmiac, is a rare naturally occurring mineral composed of ammonium chloride, NH4Cl. It forms colorless, white, or yellow-brown crystals in the isometric-hexoctahedral class. It has very poor cleavage and is brittle to conchoidal fracture. It is quite soft, with a Mohs hardness of 1.5 to 2, and it has a low specific gravity of 1.5. It is water-soluble. Sal ammoniac is also the archaic name for the chemical compound ammonium chloride.
Pliny , in Book XXXI of his Natural History, refers to a salt produced in the Roman province of Cyrenaica named hammoniacum, so called because of its proximity to the nearby Temple of Jupiter Amun (Greek However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's De re metallica In any case, that salt ultimately gave ammonia compounds their name.
The first attested reference to sal ammoniac as ammonium chloride is in the Pseudo-Geber work De inventione veritatis, where a preparation of sal ammoniac is given in the chapter De Salis armoniaci præparatione, salis armoniaci being a common name in the Middle Ages for sal ammoniac.
It typically forms as encrustations formed by sublimation around volcanic vents and is found around volcanic fumaroles seams. Associated minerals include sodium alum and other fumarole minerals. Notable occurrences include Tajikistan; and Parícutin.