A zeolite occuring in groups of glassy acicular crystals, and in masses which often have a radiated structure. It is a hydrous silicate of alumina and soda.

a group of minerals of the zeolite family consisting of a hydrous silicate of sodium and aluminum

Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula .