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.
ANNABERGITE specimens:
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ANNABERGITE specimen ann-1
$ 80.00
Dims: 2.0" x 1.5" x 0.7"(5.1 x 3.8 x 4.3cm)
Wt: 1.16 oz.( 33.0g)
Km3 Adit, Agios Constantinos, Laurion, Greece
A portion of this specimen's surface is covered with tiny clusters of Annabergite, a hydrated nickel arsenate mineral. Sometimes called "nickel bloom," this mineral occurs in lovely radiating clusters of tiny grass-green crystals. They have a pearly luster that sparkles more than gleams because of their small size- a 10-power loupe is needed to see individual crystals. They have an acicular, radiating habit and are definitely translucent, but are too small to effectively test for transparence. The host rock that these clusters rest on is a dark gray color with substantial rust-staining on it. I have not seen a specimen of Annabergite before, and am impressed with the brightness of its green coloration.
no photo
ann-1 ($ 80.00)
Km3 Adit, Agios Constantinos, Laurion, Greece
ANNABERGITE specimen ann-2
$ 45.00
Dims: 2.0" x 1.5" x 0.7"(5.1 x 3.8 x 4.3cm)
Wt: 1.16 oz.( 33.0g)
Laurion, Greece
A small pocket in the brown host rock of this specimen houses several sprays of radiating Annabergite crystals. These crystals do not exceed 2 mm in length, but are in excellent condition, being protected by the recess that they line. Their form is good, though hard to see, and they have a pearly luster. Their color is green and they are translucent. There are several other small sprays of the mineral scattered elsewhere on the host rock, but most of these appear to be incomplete or damaged. There is also a dull, pale-green patch of massive material that I cannot identify- I suppose it could be more Annabergite that was either weathered or subjected to adverse growing conditions.
no photo
ann-2 ($ 45.00)
Laurion, Greece
ANNABERGITE specimen ann-3
$ 45.00
Dims: 2.8" x 2.0" x 0.7" (7.1 x 5.1 x 1.8 cm)
Wt: 3.20 oz. (90.7 g)
Nickel Mine, Churchill County, Nevada, U.S.A.
A substantial amount of Annabergite rests on the green- and rust-colored host rock of this specimen. There is very little crystal form visible in it, so it is difficult to ascertain damage, if that concept even applies. There are a few tiny patches of radiating needles that are pressed against the host rock, along with several bits of a thin crust of the pale green material. Where crystal form is visible, there is a pearly luster, but the crusts all have a very dull luster. A substantial portion of the host rock seems to be permeated with veins of these crusts, and the rock in general in that area has a greenish coloration. Other areas of the host rock show a bright, almost rusty coloration that might be due to limonite. It is a rather odd specimen from a locality that I have never heard of before.
no photo
ann-3 ($ 45.00)
Nickel Mine, Churchill County, Nevada, U.S.A.
ANNABERGITE specimen ann-4
$ 65.00
Dims: 2.7 x 1.7 x 1.3" (6.9 x 4.3 x 3.3 cm)
Wt: 3.23 oz. (91.5 g)
KM-4 Adit, Laurion, Greece
Several tiny sprays of radiating Annabergite crystals rest in a hollow in the host rock of this specimen. The crystals are very small, as they do not exceed 0.1" (3 mm) in length, and are generally in good condition, though a few of the most exposed clusters are crushed and incomplete. Under a 10-power loupe, the crystals appear to have a good monoclinic, rhombus-shaped tabular form. They also appear to be transparent and moderately clear, though without magnification these traits cannot be determined. All have a bright green coloration and show glimpses of a pearly luster. The hollow in which they rest is lined with tabular calcite crystals that are stained a pale brown, and the host rock appears to be made of both calcite and possibly limonite.
no photo
ann-4 ($ 65.00)
KM-4 Adit, Laurion, Greece
ANNABERGITE specimen ann-5
$ 80.00
Dims: 1.3 x 0.6 x 0.5" (3.3 x 1.5 x 1.3 cm)
Wt: 10.5 g
Laurium, Greece
This small thumbnail specimen consists of a piece of pale brown host rock on which rests a druse of tiny Annabergite crystals. These crystalsdo not exceed 0.1" (3 mm) in length and tend to be less than 1 mm thick. Though a few of them are visibly damaged, most are intact and in excellent condition. Even with their rather intense intergrowth, all appear to have excellent monoclinic bladed form- their edges are well-defined and their faces are clean, possessing a bright pearly-to-vitreous luster. All have the classic bright green coloration of Annabergite and are transparent and at least moderately clear. The host rock on which they rest appears to be made of quartzite, though a single broken calcite crystal rests on it near the Annabergite druse. Other sprays of Annabergite needles rest on the other side of the host rock, but these have been coated with a glue or lacquer of some sort.
no photo
ann-5 ($ 80.00)
Laurium, Greece
ANNABERGITE specimen ann-6
$ 55.00
Dims: 2.5 x 1.6 x 1.5" (6.4 x 4.1 x 3.8 cm)
Wt: 2.54 oz. (72.0 g)
KM4 Adit, Laurion, Greece
Many nodules and sprays of tiny Annabergite blades rest in the hollows in the host rock of this speciemen. These blades do not exceed 0.1" (3 mm) in length but are generally in good condition- only the most exposed are damaged. The intact crystals appear to have excellent monoclinic form, with sharp edges and clean faces. All have the standard deep green color and bright pearly luster and are transparent and apparently quite clear, though the nodules are translucent at best. The host rock is made of a gray limestone and is rust-stained in some areas.
no photo
ann-6 ($ 55.00)
KM4 Adit, Laurion, Greece
ANNABERGITE specimen ann-7
$ 50.00
Dims: 3.1 x 1.7 x 1.5" (7.9 x 4.3 x 3.8 cm)
Wt: 5.52 oz. (156.7 g)
KM4 Adit, Laurion, Greece
Several clusters of tiny, radiating Annabergite blades rest in a crevice in the host rock of this specimen. These blades do not exceed 0.1" (3 mm) in length but are in excellent condition due to their protective surroundings. Though their size makes them difficult to study, their monoclinic form is excellent. All have the grass-green color and bright pearly luster that are standard for the species, and though individual crystals are transparent, the clusters are essentially translucent. Their base is made up of limonite that is coated with a thick layer of white, crystalline calcite.
no photo
ann-7 ($ 50.00)
KM4 Adit, Laurion, Greece
ANNABERGITE specimen ann-8
$ 50.00
Dims: 3.0 x 2.1 x 1.7" (7.6 x 5.3 x 4.3 cm)
Wt: 5.45 oz. (154.7 g)
KM4 Adit, Laurion, Greece
Many clusters of tiny Annabergite blades line a hollow in the limestone host of this specimen. The crystals that make up the clusters are tiny, not exceeding 0.1" (3 mm) in length, but are in excellent condition. Their monoclinic form is very good, and all have a grass-green coloration and are translucent to transparent, depending on their intergrowth. They rest on a creamy-white calcite crust along with what appears to be a layer of botryoidal goethite.
no photo
ann-8 ($ 50.00)
KM4 Adit, Laurion, Greece
ANNABERGITE specimen ann-9
$ 70.00
Dims: 2.1x2.1x1.25" (5.2x5.3x3.2 cm)
Wt: 3.4 oz. (96.5g)
Plaka Mine, Laurium, Greece
This specimen shows the characteristic green of annabergite against a yellow-tan background mineral that I have not identified. Under a loupe, it is apparent that many different minerals are on this specimen, and that the annbergite occurs as tiny transparent bladed crystals with trapazoidal terminations. The clarity of these crystals (with their prismatic shape) gives them a nice druzy sparkle.
no photo
ann-9 ($ 70.00)
Plaka Mine, Laurium, Greece
 

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