Natrolite is a tectosilicate mineral, in the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10 . 2H2O[3] . The specimens locality is not known, but the type locality is basaltic rock. From a base rock of basalt, prismatic dirty white to colourless crystals, with a hint of green at their bases, have obviously grown into a cavity,