Rodolicoite , Grattarolaite Locality: Castelnuovo Mine, Santa Barbara lignite District, Cavriglia, Valdarno (Val d'Arno), Arezzo Province, Tuscany, Italy Brown crystals of Rodolicoite intimately intergrown with Grattarolaite, pseudo after Vivianite. Field of view 3 mm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Grattarolaite
Grattarolaite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe³⁺₃O₃(PO₄).
It crystallizes in the hexagonal crystal system (space group R3m).
Key properties: specific gravity 4.08; Brown streak; Greasy luster.
IMA symbol Gra, IMA status: approved, named in 1995.
Very rare, in microcrystalline nodules in lignite beds which appear to have burned naturally.
It is found associated with Rodolicoite, heterosite.
The mineral was named to honor Giuseppe Grattarola (1844–1907), Professor of Mineralogy, Florence University, Florence, Italy.