Stilbite is a tectosilicate mineral of the zeolite group consisting of hydrated calcium aluminium silicate, NaCa2Al5Si13O36·14H2O.Usually a small proportion of the calcium is replaced by sodium. Crystals are monoclinic, and are commonly twinned, giving rise to complex groups and characteristic sheaf-like aggregates. The color is usually white, sometimes red, and on the perfect cleavage (parallel to the plane of symmetry) the lustre is markedly pearly; hence the name stilbite, from Greek, "to shine". After the separation of heulandite from this species in 1818, the name desmine ("a bundle") was proposed, and this name is now employed in Germany. The hardness is 3.5 - 4 and the specific gravity 2.2. The sievelike crystal structure of the zeolite stilbite enables it to separate hydrocarbons in the process of petroleum refining.

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