They are similar and hard to distinguish when in clusters with radiating, acicular habits. Natrolite forms thinner crystals with pyramidal terminations, and mesolite's fiber-like crystals are usually the thinnest crystals of the three minerals. Scolecite's larger crystals tend to be more robust and durable. These characteristics are only generalities and can not be used as dependable identifying traits. Absolute identification can not be made by ordinary means.
Color is clear or white.
Luster is vitreous. Also nodules, fibrous and earthy masses. Cleavage is perfect in two directions, prismatic. Cleavage is rarely seen due to small crystal size. Fracture is conchoidal to uneven.