They are found in serpentine and, especially where the lavas contain nepheline or leucite, are often rich in zeolites, such as analcite, prehnite, natrolite, scolecite, chabazite, heulandite, etc.
12.
Though not a zeolite, prehnite is found associated with minerals such as datolite, calcite, apophyllite, stilbite, laumontite, heulandite etc . in veins and cavities of basaltic rocks, sometimes in granites, syenites, or gneisses.
13.
Small, lustrous, white or pink, pointed blades of stilbite-Na, and formless masses, up to 5 cm in diameter, have been found there, covering a thin crust of reddish heulandite in large fractures and cavities in the highly weathered volcanic andesite or rhyolite.
