RUIFRANCOITE on MUSCOVITE (thumbnail)

Ruifrancoite, with the chemical formula Ca2(□,Mn2+)2(Fe3+,Mg,Mn2+,Fe2+,Al)4Be4(PO4)6(OH)4(OH,H2O)2·4H2O, is a recently and extremely rare identified member of the roscherite group, characterized by its monoclinic crystal system. This mineral is found as a late-stage vug-filling component within albite and muscovite, and it is commonly associated with cyrilovite and meurigite in the granite pegmatite located at the Sapucaia (Proberil) mine in Sapucaia do Norte, Galiléia County, Minas Gerais, Brazil. Ruifrancoite typically appears in the form of needles or laths that measure between 1 to 2 μm in thickness and can reach lengths of up to 100 μm, often arranged in fan-shaped botryoidal clusters. It exhibits a reddish-brown color, an orange-brown streak, and a vitreous luster, while being transparent and lacking fluorescence.