Annabergite
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| Annabergite | |
|---|---|
 Annabergite (green) from Lavrion, Greece | |
| General | |
| Category | Arsenate minerals |
| Formula | Ni3(AsO4)2·8H2O |
| IMA symbol | Anb[1] |
| Strunz classification | 8.CE.40 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/m |
| Unit cell | a = 10.179(2), b = 13.309(3) c = 4.725(1) [Å]; β = 105(1)°; Z = 2 |
| Identification | |
| Color | Apple-green, pale green, pale rose or pale pink, white, gray; may be zoned |
| Crystal habit | Usually as fibrous veinlets, crystalline crusts, or earthy; rare as well formed crystals |
| Cleavage | Perfect on {010}, indistinct on {100} and {102} |
| Tenacity | Sectile |
| Mohs scale hardness | 1.5–2.5 |
| Luster | Subadamantine, pearly on cleavages, may be dull or earthy |
| Streak | Pale green to white |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.07 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.622 nβ = 1.658 nγ = 1.687 |
| Birefringence | δ = 0.065 |
| 2V angle | Measured: 84° |
| References | [2][3][4] |
Annabergite is an arsenate mineral consisting of a hydrous nickel arsenate. It is considered a member of the vivianite group and known for its ability to form crystals in a characteristic apple-green color.
Annabergite has been known since the 18th century, although type localities were not published along initial descriptions. The first report of Annabergite by Axel Fredrik Cronstedt from 1758 erroneously identifies it as a nickel oxide mineral and assigned it the latinized name Ochra niccoli, while Wallerius gave it the name nickel bloom in 1778. Annabergite was thoroughly described in 1852 by Brooke and Miller[3] from specimens found in Annaberg in Saxony, which was proposed as namesake for the mineral.
