They are similar and difficult to distinguish when in clusters with radiating, acicular habits. Natrolite tends to forms thin crystals with pyramidal terminations, but mesolite's fiber-like crystals are usually the thinnest of the three. Scolecite's larger crystals tend to be more robust and durable. Luster is vitreous to dull on some compact masses. Also nodules, fiberous and massive crusts.
Cleavage is perfect in two directions, prismatic.
Cleavage is rarely seen due to small crystal size. Fracture is conchoidal. Hardness is 5 - 5.5. Streak is white. Associated Minerals are quartz , apophyllite , benitoite , heulandite , stilbite and other zeolites .