Annabergite
Annabergite is just a known person in the Vivianite Group of minerals which includes Annabergite, Erythrite and Vivianite and others. Annabergite is frequently discovered in stunning shades of bright, apple green. This colour that is characteristic easily noticed and was utilised by miners to spot veins of nickel-bearing ore. Annabergite is really a product of weathering nickel. Where weathered nickel and cobalt ores are observed both Annabergite and Erythrite are often used to spot veins of the two cores. Annabergite has been called “Nickel Bloom” by miners referring to its bright crystals that are green. Likewise, Erythrite is often called “Cobalt Bloom” for the bright crystals being reddish-purple. Annabergite is isostructural with Erythrite. Isostructural means the two minerals have the structure that is same different chemistries.
Well developed Annabergite crystals are fairly unusual as it is frequently found as fibrous veinlets or crystalline crusts. Specimens are attractive because of the bright colour that is green associated minerals such as metallic Gersdorffite. When crystals are located they are far too small for faceting. The image above shows a Gersdorffite that is faceted treasure a vein of Annabergite running all the way through it.
Annabergite was named by Henry J. Brooke and William Hallowes Miller in 1852 after one of the type locality, Annaberg, Saxony, Germany.
Annabergite distribution: many localities, but typically in lower amounts. In Germany, from Annaberg and Schneeberg, Saxony; at Richelsdorf, Hesse. From Dobšiná (Dobschau), Slovakia. At Leogang, Salzburg, Austria. In the Sierra Cabrera, Almería Province, and at Molvizar, Granada Province, Spain. In England, in the Dolcoath mine, Cornwall; through the Coniston mines, Coniston, Cumbria. At Strathclyde and Galloway, Leadhills-Wanlockhead district, Scotland. Fine examples through the Kamariza, Plaka, and Verzekos mines, and along the road to Laurium, Greece. From the Bou Azzer district, Morocco. In the Tchah Shurch, and at the Talmessi mine, Anorak region, Iran. During the Los Angeles Sorpresa mine, Tapacari, Cochabamba, Bolivia. In the Gloria mine, Alisito, Sinaloa, Mexico. In America, at the Ore Hill Mine, Pacoima Canyon, Los Angeles County, as well as in the Kalkar Quarry, Santa Cruz, Santa Cruz County, California; from the Nickel and Lovelock mines, Table Mountain district, Churchill County, Nevada; during the Snowbird Mine, Mineral County, Montana; as well as in the Alhambra Mine, Grant County, New Mexico. At Cobalt, Ontario, Canada. In the 132 North deposit, Widgiemooltha district, Western Australia, as well as a few localities into the Flinders Ranges, Southern Australia. From the Horai mine, Hyogo Prefecture, and at Kuchisaka, Osaka Prefecture, Japan.
| Category: | Arsenate minerals Vivianite group |
| Chemical Formula: | Ni3(AsO4)2 • 8H2O |
| Hydrated Nickel Arsenate | |
| Molecular Weight: | 598.03 gm |
| Composition: | Nickel | 29.44 % | Ni | 41.48 % | Ni2O3 |
| Arsenic | 25.06 % | As | 38.43 % | As2O5 | |
| Hydrogen | 2.70 % | H | 24.10 % | H2O | |
| Oxygen | 42.81 % | O | |||
| 100.00 % | 104.01 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Rare crystals, typically poorly formed, elongated along [001], flattened on [010], with {001}, {010}, {100}, several modifying forms, to 5 mm; usually as fibrous veinlets, crystalline crusts, or earthy. |
| Twinning: | None |
| Cleavage: | Perfect on {010}; indistinct on {100}, {102}; translation gliding on T{010}, t[001] |
| Fracture: | Irregular/Uneven Conchoidal Fibrous Hackly Micaceous None observed Splintery Step-like Sub-Conchoidal |
| Tenacity: | Sectile; flexible in thin {010} laminae |
| Moh’s Hardness: | 1.5 – 2.5; softest on {010} |
| Density: | 3.07 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Colour: | Apple green, light grey to light apple green, white; pale rose red when rich in cobalt. Colour may be light pink or light rose at Co: Ni ~1:1 (50-50 rule), then becomes white or gray, pale green, and apple-green in the Annabergite end of the series. May be zoned. |
| Transparency: | Transparent to translucent |
| Luster: | Sub-Adamantine; pearly on {010} cleavages, may be dull or earthy when massive |
| Refractive Index: | 1.622 – 1.687 usually Biaxial (+), may be Biaxial (–) |
| Birefringence: | 0.065 |
| Dispersion: | Relatively weak, r > v |
| Pleochroism: | None |
