Umbrianite, K7Na2Ca2[Al3Si10O29]F2Cl2, a new mineral species from melilitolite of the Pian di Celle volcano, Umbria, Italy

Abstract: The new mineral umbrianite, ideally K7Na2Ca2[Al3Si10O29]F2Cl2, was discovered as an essential groundmass mineral in melilitolite of the Pian di Celle volcano, Umbria, Italy. It forms rectangular, lamellar or lath-shaped crystals (up to 25 30 200 mm), typically flattened on {010}, and sheaf-like aggregates (up to 200–500 mm across). Umbrianite is commonly associated with kalsilite, leucite, fluorophlogopite, melilite, olivine (Fo.60), diopside, nepheline, Ti-rich magnetite, fluorapatite, cuspidine–hiortdahlite series minerals, götzenite, khibinskite, monticellite–kirschsteinite series minerals, westerveldite, various sulphides and peralkalin