Mesolite: Gemstone Information

Mesolite is Na2Ca2(Al6Si9O30)8H2O and a orthorhombic member of the zeolite mineral group. It forms translucent to transparent elongated white or colourless invariably twinned prismatic crystals, may be stalactitic or occur in porcellanous masses with hardness 5 and two directions of perfect cleavage. The SG is 2.27 and the RI for the alpha, beta and gamma rays is 1.5048, 1.5050 and 1.5053, biaxial positive with birefringence 0.001. Mesolite occurs with natrolite (q.v.), scolecite, other zolites and calcite in cavities of volcanic rocks, especially basalt. Fashioned crystals with a characteristic silky lustre may have come from the outstanding crystals found in the Pashan Hills in the Poona area of India.