Fianelite

Fianelite is a mineral belonging to the manganese vanadate category, found in iron-manganese ores. Named after the place where it was found, Fianel, a mine located in Val Ferrera (Ferrera valley), in the canton of Graubünden, Swiss. This mineral is found in small amounts in metamorphosed iron-manganese ores. This is the last crystallization of vanadate at the site since medaite was the last vanadate mineral being crystallized, but because of retrograde metamorphism, occurring at the place, vanadium moved into medaite veinlets, forming cross-cutting fianelite on medaite.

Occurrence

This mineral is found in the Suretta nappe which is composed of three main units going from a quartzite base to dolomitic and calcitic marble, to a calcschist top. Fianelite is only found at the Triassic dolomitic and calcitic marbles unit which contains metamorphosed iron and manganese ores. Fianelite is found as small fractures of less than 1 mm in size in association with quartz, aegirine, and iron hydroxide-oxides like limonite. These fractures are found cross-cutting veinlets, which are made out of quartz, rhodonite, kutnohorite, aegirine, parsettensite, and different vanadium minerals, that are at the same time cross-cutting lenses of medaite-rich rocks which are found in the iron and manganese ores.

Physical properties

Fianelite's crystals grow in polycrystalline crusts and rosettes that can measure up to 2.5 mm in diameter, and when strangely found as single crystals, they can measure up to 0.2 mm in diameter. It presents good parallel cleavage on {001} and {100}.