A few very small white crystals of the very rare mineral vertumnite from the TL in Italy (Campomorto Quarry, Montalto di Castro, Viterbo Province, Lazio, Italy). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Vertumnite
Vertumnite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₄Al₄Si₄O₆(OH)₂₄·3H₂O.
It crystallizes in the hexagonal crystal system (space group P6_3/m).
Key properties: Mohs hardness 5; specific gravity 2.15; Vitreous luster; optically biaxial.
IMA symbol Vtn, IMA status: approved, named in 1975.
Occurs as late-forming crystals inside a small cavity in phonolite.
It is found associated with Tobermorite, ettringite.
The name refers to Vertumnus, the god worshipped by the ancient Etruscan people who inhabited the region where the mineral was found.