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 from Bombay, Hunterian Museum, Glasgow.jpg
Mesolite from Bombay collected in the 18th century by Dr John Hunter
(repeating unit)
IMA symbolMes[1]
Strunz classification9.GA.05
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
(same H-M symbol)
Space groupFdd2
Unit cella = 18.4049(8) Å,
b = 56.655(6) Å,
c = 6.5443(4) Å; Z = 8
ColorColorless, white, gray, yellowish brown
Crystal habitAs elongated prismatic crystals, commonly in hairlike tufts and aggregates of fibers; radiating compact masses; stalactitic; porcelaneous
TwinningCharacteristically twinned on {010} or {100}
CleavagePerfect on {110} and {110}
TenacityBrittle, masses tough
Mohs scale hardness5
LusterVitreous, silky when fibrous
DiaphaneityTransparent to translucent, opaque
Specific gravity2.26
Optical propertiesBiaxial (+)
Refractive indexnα = 1.505 nβ = 1.505 nγ = 1.505
Birefringenceδ = 0.001
2V angleMeasured: 80°
Other characteristicsMay exhibit a small pyroelectric effect; piezoelectric

Mesolite crystallizes in the orthorhombic system and typically forms fibrous, acicular prismatic crystals or masses.[3] 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.


It was first described in 1816 for an occurrence in the Cyclopean Islands near Catania, Sicily.[5] From the Greek mesos, "middle", as its composition lies between natrolite and scolecite.[4][5] Like other zeolites, mesolite occurs as void fillings in amygdaloidal basalt also in andesites and hydrothermal veins.[3]



  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ a b c Handbook of Mineralogy
  4. ^ a b
  5. ^ a b c Webmineral data