Outstanding pale purple crystals of the very rare mineral giuseppettite from the type locality (Biachella Valley, Sacrofano, Rome, Latium, Italy) and only one of the three confirmed localities worldwide — Photo: David Hospital · CC BY-SA 4.0
Giuseppettite
Giuseppettite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₄₂K₁₆Ca₆Si₄₈Al₄₈O₁₉₂(SO₄)₁₀Cl₂·5H₂O.
It crystallizes in the hexagonal crystal system (space group P31c). It is a member of the Cancrinite-sodalite structural group.
Key properties: Mohs hardness 6–7; specific gravity 2.35; optically uniaxial.
IMA symbol Giu, IMA status: approved, named in 1979.
Occurs as veinlets in a block of sanidinite volcanic ejecta.
It is found associated with Potassic feldspar, nepheline, häuyne, biotite, kalsilite.
The mineral was named to honor Giuseppe Giuseppetti, Professor of Mineralogy, University of Pavia, Pavia, Italy.