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The Mineral annabergite

Bright Green Annabergite Pocket

Annabergite is a rare nickel mineral that can often has a bright green color. It is the end member of a series with Erythrite, with Annabergite being the nickel-dominant member and Erythrite being the cobalt-dominant member. Annabergite often contains some cobalt in its structure. The color caused by cobalt will dominate, and will cause some Annabergite to have a purplish color even if there is less cobalt than nickel present. Annabergite is named after the locality of Annaberg, Saxony, Germany, which is a type locality for this mineral.

Chemical Formula

Ni₃(AsO₄)₂ · 8(H₂O)

Color

Bright green, apple-green, purplish-green, beige, gray, grayish-pink.

Crystal System

Monoclinic

Properties

Streak
Light green

Hardness
1.5 - 2.5

Transparency
Transparent to translucent

Specific Gravity
3.0 - 3.1

Luster
Vitreous, pearly. Earthy specimens may be dull.

Cleavage
1,1

Fracture
Splintery

Tenacity
Slightly sectile and flexible

Crystal Habits

Never in large crystals; most often encrusting and in small botryoidal groups lining cavities. Also in groups of fragile radiating, acicular, or fibrous groupings, in rounded spiky balls, earthy, and massive. Individual microcrystals are thin and bladed, with a distinctly angled termination and usually with growth layers or striations.

Additional Information

Composition
Hydrous nickel arsenate, often with some cobalt

In Group
Phosphates; Arsenates

Striking Features
Color, crystal habits, and streak.

Environment
As a secondary mineral that forms as an alteration product in the oxidation zone of nickel ore and cobalt sulfide deposits.

Rock Type
Sedimentary, Metamorphic

Other Names

	Cabrerite	Synonym of Annabergite. May also refer to the distinctly crystallized form that comes from Lavrion, Greece, or may refer to a magnesium-rich variety. Named after the Sierra Cabrera in Spain.
	Nickel Bloom

Uses

Annabergite is a minor ore of nickel in nickel deposits.

Noteworthy Localities

Annabergite is not a common mineral. The only significant specimen locality of Annabergite is Lavrion, Greece, where it occurs in small bright-green, yet visible crystals. Other Annabergite localities include Cobalt, Timiskaming District, Ontario, Canada; and Cottonwood Canyon, Humboldt County, Nevada.