A feldspathoid mineral and member of the sodalite group Na8[Al6Si6O24]SO4, where it is closely related to haüyne; sp. gr. 2.3–2.4; hardness 5.5–6.0; cubic; grey, white, or greenish, often with light-blue tinges; vitreous lustre; crystals, when present, rhombododecahedra, but it is also massive; cleavage poor, rhombododecahedral; occurs in extrusive alkaline undersaturated (see silica saturation) igneous rocks such as nosean leucitophyres and phonolites.