THE MINERAL ANNABERGITE

  • Chemistry: Ni3(AsO4)2-8(H2O) , Hydrated Nickel Arsenate
  • Class: Phosphates
  • Group: Vivianite
  • Uses: A very minor ore of nickel and mineral specimens
  • Specimens

Annabergite has a wonderful, bright green color. This characteristic color is easily noticeable and was used to spot veins of nickel-bearing ore. Annabergite, or "Nickel Bloom" as it is called by miners, is a weathering product of nickel-containing minerals such as niccolite, NiAs. Where weathered cobalt and nickel ores are found, both erythrite, Co3(AsO4)2-8(H2O) and annabergite are important markers. Erythrite, called "Cobalt Bloom", is bright red-purple and is isostructural with annabergite. Isostructural means that the two minerals have the same structure but different chemistries. The two minerals are actually in a series where the nickel and cobalt ions can substitute freely for each other. When the two ions are in near-equal concentrations, the resulting color is gray or off-white. A third mineral is also isostructural with annabergite and is called kottigite or koettigite, Zn3(AsO4)2-8(H2O). However, the series is incomplete, meaning that the zinc and nickel ions only substitute for each other on a very limited basis. Most annabergite is found in a crust or powder form, but a few specimens from Greece show small, well-shaped crystals. This mineral, when found in fine green crystals, can be rather attractive.

PHYSICAL CHARACTERISTICS:

  • Color is bright apple green to pale green or gray in massive and thin crust forms.
  • Luster is vitreous to adamantine to dull in massive or powdered forms.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include flattened striated blades or radiating accicular crystals, but large crystals are extremely rare. More commonly as crusts or powdery masses.
  • Cleavage is perfect in one direction.
  • Fracture is flaky.
  • Hardness is 1.5 - 2.5
  • Specific Gravity is approximately 3.0 - 3.1 (average for translucent minerals)
  • Streak is pale green or gray, in gray specimens.
  • Associated Minerals are niccolite, skutterudite, gersdorffite and erythrite.
  • Other Characteristics: Thin flakes are flexible.
  • Notable Occurrences include Cobalt, Ontario; Lavrion, Greece; Humboldt, Nevada, USA; Sierra Cabrera, Spain and Germany.
  • Best Field Indicators are color, softness, associations, and flexible crystals.
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Available ANNABERGITE specimens:
see this List of ALL specimens including SOLD ones

 

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