Heulandite is the name of a series of tecto-silicate minerals belonging to the zeolite group. Previously recognized as an individual mineral species, it was reclassified as a series name by the International Mineralogical Association in 1997. Heulandite typically occurs alongside stilbite and other zeolites in the amygdaloidal cavities of basaltic volcanic rocks, as well as occasionally in gneiss and hydrothermal veins.
