Cabrerite - Encyclopedia

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

Cabrerite is a magnesian variety of annabergite (up to 6% MgO). Remember that annabergite is a rare secondary mineral from the oxidation zone of nickel-cobalt deposits where it results 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. Cabrerite takes its name from its place of discovery : La Sierra da Cabreira (Portugal). Like annabergite it never forms large crystals (maximum 10 mm): they are usually prismatic to acicular and striated according to [001]; it appears mainly in powdery coatings composed of fine flattened needles on {010}, in earthy aggregates, or in masses that can exceed a kilo. Adamantine luster, it has a pale green to apple green color which is its main criterion of distinction.

Main photo : Cabrerite from KM 3 Mines, Lavrion, Greece © Henry Minot

Cabrerite in the World

The most beautiful known samples of cabrerite come from the Lavrion mines (Greece), which produced almost centimeter-sized crystals, often forming fan-shaped aggregates, implanted on calcite. It is also known in the Sierra de Cabreira (Portugal), its type locality.

Right photo : Cabrerite from KM 3 Mines, Lavrion, Greece © Alexandros Frantzis

Cabrerite in France

Cabrerite is not present in the French underground.


No twin known for this mineral species.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 1.5 to 2.5
Density : 3.07
Fracture : Irregular
Streak : White to pale green

TP : Translucent to transparent
RI : 1.622 to 1.687
Birefringence : 0.065
Optical character : Biaxial (+/-)
Pleochroism : None
Fluorescence : None

Solubility : Acids

Magnetism : None
Radioactivity : None