Pale brown prismatic crystals of the very rare mineral ciprianiite from the type locality and only one of the two known localities worldwide: Tre Croci, Vico Lake, Viterbo Province, Latium, Italy. — Photo: David Hospital · CC BY-SA 4.0
Ciprianiite
Ciprianiite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₄(ThCa)Al(Be₀.₅ ₁.₅)Σ₂[B₄Si₄O₂₂](OH)₂.
It crystallizes in the monoclinic crystal system (space group P2/a). It is a member of the Hellandite structural group.
Key properties: White streak; Vitreous luster.
IMA symbol Cip, IMA status: approved, named in 2001.
Found in miarolitic cavities and voids in alkali-syenitic pyroclastic ejecta. Formed by late- stage post-magmatic hydrothermal fluids enriched in Zr, Ti, REEs, and actinide elements.
It is found associated with Sanidine, plagioclase (An 20-80%), feldspathoid, clinopyroxene, clinoamphibole, magnetite, titanite, zircon, danburite, thorite, fluorite, tourmaline.
The mineral was named to honor Curzio Cipriani, Professor of Mineralogy and Head of the Museum of Mineralogy, (later of Natural History), University of Florence, Italy.