Radial Annabergite Crystals From Greece
Radial Annabergite Crystals From Greece. Photo Credit: László Tóth

Annabergite is an arsenate mineral consisting of a hydrous nickel arsenate, crystallizing in the monoclinic system and isomorphous with vivianite and erythrite.
Formula: Ni3(AsO4)2·8H2O 
System: Monoclinic
Colour: Green, light grey

From Lavrio; Greece
Crystals are minute and capillary and rarely met with, the mineral occurring usually as soft earthy masses and encrustations. A fine apple-green color is its characteristic feature.