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