natrolite

Natrolite is a tectosilicate mineral of the zeolite group with the chemical formula Na2Al2Si3O10·2H2O. It crystallizes in the orthorhombic system and typically forms slender prismatic to needle-like crystals that occur in radiating or fibrous aggregates. Color is usually colorless to white, though impurities can produce pale yellow, pink, or blue tints. The hardness is about 5 to 5.5 and the specific gravity is around 2.2.

The mineral’s structure consists of a three-dimensional framework of interconnected SiO4 and AlO4 tetrahedra with channels that host water molecules and sodium cations. This porous framework is a hallmark of zeolites and underlies natrolite’s ion-exchange and adsorption properties.

Formation and occurrence: Natrolite forms by low-temperature hydrothermal alteration of silicate rocks, particularly basalts and rhyolites, in vesicles and amygdales, and in other zeolitic environments. It is commonly associated with other zeolites such as analcime, stilbite, mesolite, and scolecite.

Uses and significance: In hand specimens natrolite is collected as a mineral specimen and studied for its crystal chemistry and zeolite behavior. While zeolites are widely used industrially for adsorption and ion exchange, natrolite itself is less common as a commercial material and is primarily of interest to collectors and researchers as part of zeolite mineral studies.