ANNABERGITE (from the name of the "Annaberg" deposit within the Ore mountains, Saxony, East Germany * EN: annabergite, nickel bloom; DE: Annabergit; FR: nickelocre; annabergite; ES: anabergita; RU: аннабергит) is the mineral of the class of arsenates, Ni3[AsO4]2 • 8H2O. It often contains Co. It is the end member of the continuous isomorphous series of annabergite - erythrite. The admixtures are: Ca, Mg, Fe, Zn. It crystallizes into the monoclinic crystal system. The structure is sub-layered. It forms crusts, efflorescences, incrustations, earthy aggregates. The colour is apple, pale, or dirty green, to white, in case of the replacement of the significant part of Ni to Ca. The lustre is vitreous, dim for the earthy varieties. The hardness is 2.5-3. The density is 3050±50 kilograms per cubic metre. It is the supergene mineral. It is formed on the account of the oxidation of the arsenic-containing minerals of Ni.

Annabergite is the prospecting indicator for the nickel ores.