Annabergite Locality: Km-3 Mine, Lavrion Mines, Lavrion (Laurion; Laurium), Lavrion District Mines, Lavrion (Laurion; Laurium) District, Attikí (Attica; Attika) — Photo: Didier Descouens · CC BY-SA 3.0
Annabergite
Also known as: Nickel bloom.
A hydrous nickel arsenate famous for its bright apple-green crusts, formed where nickel ores weather.
Intro adapted from Wikipedia (CC BY-SA).
Annabergite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Ni₃(AsO₄)₂·8H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Vivianite structural group.
Key properties: Mohs hardness 1.5–2.5; specific gravity 3.07; typically green or yellow or white; Pale green to white streak; Subadamantine, pearly on cleavages, may be dull, earthy luster; refractive index 1.656; optically biaxial.
IMA symbol Anb, grandfathered status — known before the IMA’s founding, named in 1852.
An uncommon secondary mineral, formed by the alteration of Co–Ni-bearing arsenides and sulfides, in the oxidized zone of hydrothermal mineral deposits.
It is found associated with Erythrite, retgersite, gersdorffite, nickeline, maucherite, nickel-skutterudite.
The name refers to its originally noted occurrence at Annaberg, Germany.
Collections: Collector Favorites, Rare & Remarkable.