Stellerite is a zeolite mineral that crystallizes in the orthorhombic system, usually as radiating, rounded nodules or sheaf-like aggregates of thin, platy, dipyramidal crystals. It has a Mohs hardness of 4.5, perfect cleavage in one direction, and a specific gravity of 2.2. Stellerite is a secondary mineral that occurs almost exclusively in the amygdaloidal cavities of basaltic volcanic rocks. It is translucent to transparent and usually white or colorless, although impurities can impart a range of pale hues.
