23 Photos
Mesolite
Chemical Formula	Na2Ca2(Al2Si3O10)3·8H2O
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	5
Specific Gravity	2.26
Color	Colorless, white, gray, yellowish
Streak	White
Luster	Vitreous
Refractive Index	n = 1.505 n = 1.505 n = 1.505
Diaphaneity	Transparent, Translucent, Opaque
Cleavage	PerfectPerfect on
Fracture	Irregular/Uneven
Crystal Habit：As elongated prismatic crystals, commonly in hairlike tufts and aggregates of fibers; radiating compact masses; stalactitic; porcelaneous
Geological Setting：In cavities in basalts.

Mesolite is a tectosilicate mineral with formula Na₂Ca₂(Al₂Si₃O₁₀)₃·8H₂O. It is a member of the zeolite group and is closely related to natrolite which it also resembles in appearance.

Mesolite crystallizes in the orthorhombic system and typically forms fibrous, acicular prismatic crystals or masses. Radiating sprays of needlelike crystals are not uncommon. It is vitreous in luster and clear to white in color. It has a Mohs hardness of 5 to 5.5 and a low specific gravity of 2.2 to 2.4. The refractive indices are nα=1.505 nβ=1.505 nγ=1.506.

Occurrence

It was first described in 1816 for an occurrence in the Cyclopean Islands near Catania, Sicily. From the Greek mesos, "middle", as its composition lies between natrolite and scolecite. Like other zeolites, mesolite occurs as void fillings in amygdaloidal basalt also in andesites and hydrothermal veins.