Mesolite crystal on display at the Natural History Museum in Los Angeles, California — Photo: Jengod · CC BY-SA 3.0
Mesolite
A fibrous zeolite of the natrolite subgroup — a sodium-calcium aluminosilicate forming delicate needles in basalt cavities.
Intro adapted from Wikipedia (CC BY-SA).
Mesolite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂Ca₂(Si₉Al₆)O₃₀·8H₂O.
It crystallizes in the orthorhombic crystal system (space group Fdd2). It is a member of the Natrolite structural group.
Key properties: Mohs hardness 5; specific gravity 2.26; typically white or colorless; white streak; Vitreous, silky when fibrous luster; refractive index 1.505; optically biaxial.
IMA symbol Mes, IMA status: approved, named in 1813.
Found in cavities of volcanic rocks, typically basalt, also in andesites, porphyries, and hydrothermal veins.
It is found associated with Natrolite, scolecite, other zeolites, calcite.
Its name comes from the Greek for middle, alluding to its composition intermediate between natrolite and scolecite.
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