THE MINERAL ANNABERGITE


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:

 

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