Perfectly developed tabular pale brown mottanaite-(Ce) crystals, a very rare mineral known worldwide only from two close localities in Latium, Italy (Tre Croci, Vetralla, Vico Lake, Viterbo Province). Ex.Bernabe collection. — Photo: David Hospital · CC BY-SA 4.0
Mottanaite-(Ce)
Mottanaite-(Ce) is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₄Ce₂Al(Be₁.₅ ₀.₅)Σ₂[B₄Si₄O₂₂]O₂.
It crystallizes in the monoclinic crystal system (space group P2/a). It is a member of the Hellandite structural group.
Key properties: specific gravity 3.61; White streak; Vitreous luster; optically biaxial.
IMA symbol Mot-Ce, IMA status: approved, named in 2001.
Found in miarolitic cavities and voids in feldspathoid-bearing 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 Britholite-(Ce), sanidine, plagioclase (An 20-80%), nepheline, biotite, clinopyroxene, titanian andradite, magnetite, zircon, titanite, baddeleyite.
The mineral was named to honor Annibale Mottana, Professor of Mineralogy, University of Roma Tre (Italy), for his leadership and support of investigations and cataloguing of Latium minerals.