The structure actually contains open channels that allow water and large ions to travel into and out of the crystal structure. The size of these channels controls the size of the molecules or ions and therefore a zeolite like epistilbite can act as a chemical sieve, allowing some ions to pass through while blocking others. Color is colorless, white, pink and reddish. Luster is vitreous. Crystals are transparent to translucent.
Cleavage is perfect in one direction.
Fracture is uneven. Hardness is 4. Streak is white. Associated Minerals are quartz , beryl , calcite , yugawaralite , heulandite , stilbite and other zeolites .