Photo: Minerat/e-rocks

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. The Salammoniac is a rare mineral composed of ammonium chloride. The crystals are very well shaped and translucent. It has marvelous turquoise-blue color and waxy luster. 

Crystal system: Isometric
Formula: NH₄Cl
Crystal habit: Crystals skeletal or dendritic; massive, encrustations
Color: White, light gray, light yellow
Environment: In volcanic fumarole deposits of fresh eruptions, where rainfall that would have melted the crystals had not yet occurred. Also in underground burning coal seams in lignite deposits.

From: Unspecified Pit, La Negra, Antofagasta Province, Antofagasta Region, Chile