Class : Carbonates, nitrates, borates
    Subclass : Borates
    Crystal system : Orthorhombic
    Chemistry : Fe₃BO₅
    Rarity : Rare

Vonsenite, iron-bearing, forms a continuous series with ludwigite, magnesian. It is found in iron-copper skarns, more rarely tungsten-molybdenum, where it can constitute an industrial source of boron. It is also found in carbonate xenoliths ejected by Italian volcanoes. Vonsenite seems rarer than ludwigite. It was named in honor of the American collector Magnus Vonsne, who donated his collection to the California Academy of Sciences. It is a borate that crystallizes in long, often acicular crystals, greenish-black to black in color, sometimes generating fibrous clusters, and vaguely evokes iron-bearing tourmalines.

Main photo : Vonsenite from La Fossa, Vulcano, Aeolian Islands, Italy © Elmar Lackner

No twinning known for this mineral species.

No fakes listed for this mineral species.