Montesommaite

Montesommaite is a very rare zeolite group mineral only known from 4 quarries in the Montesomma, Somma-Vesuvius complex (Campania, Italy). It occurs in this specimen as colorless gemmy crystals. — Photo: David Hospital · CC BY-SA 4.0

Montesommaite

Montesommaite is an IMA-recognized mineral species in the silicate class, with the chemical formula K₉(Si₂₃Al₉)O₆₄·10H₂O.

It crystallizes in the tetragonal crystal system (space group I4_1/amd).

Key properties: specific gravity 2.34; White streak; Vitreous luster; optically biaxial.

IMA symbol Mtso, IMA status: approved, named in 1988.

Found in volcanic scoria.

It is found associated with Dolomite, calcite, chabazite, natrolite.

The name refers to Monte Somma, the volcano ancestral to Vesuvius, Italy, in the remnants of which the mineral occurs.