Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated Arsenates
    Crystal system : Monoclinic
    Chemistry : Ni₃(AsO₄)₂ 8H₂O
    Rarity : Rare

Annabergite is a rare secondary mineral from the oxidation zone of nickel-cobalt deposits where it results in particular from the oxidation of skutterudite and cobaltite. Since cobalt can completely replace nickel, annabergite forms a continuous series with erythrite, which has the same crystal structure. Its name comes from its place of discovery : the locality of Annaberg in Germany. It is a mineral that never forms large crystals (maximum 1 cm): they are prismatic to acicular and striated according to [001]; it appears mainly in powdery coatings composed of fine needles flattened on {010}, in earthy aggregates, or in masses that can exceed one kilogram. With an adamantine luster, it has a pale green to apple green color which is its main criterion of distinction. However, the pink color due to the cobalt quickly obliterates the green tint of the nickel and many pink cobaltiferous annabergites are wrongly considered as erythrites.

Main photo : Annabergite from Lavrion, Greece © Stephan Wolfsried

No known twins for this mineral species

No fake identified for this mineral species but very difficult to differentiate from erythrite without chemical analysis if the color is pink.