Annabergite

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Annabergite
Mineraly.sk - annabergit 2.jpg
Annabergite, Dobšiná, Slovakia
General
CategoryArsenate minerals
Vivianite group
Formula
(repeating unit)
Ni3(AsO4)2·8H2O
Strunz classification8.CE.40
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 10.179(2), b = 13.309(3)
c = 4.725(1) [Å]; β = 105(1)°; Z = 2
Identification
ColorApple-green, pale green, pale rose or pale pink, white, gray; may be zoned
Crystal habitUsually as fibrous veinlets, crystalline crusts, or earthy; rare as well formed crystals
CleavagePerfect on {010}, indistinct on {100} and {102}
TenacitySectile
Mohs scale hardness1.5 – 2.5
LusterSubadamantine, pearly on cleavages, may be dull or earthy
StreakPale green to white
DiaphaneityTransparent to translucent
Specific gravity3.07
Optical propertiesBiaxial (-)
Refractive indexnα = 1.622 nβ = 1.658 nγ = 1.687
Birefringenceδ = 0.065
2V angleMeasured: 84°
References[1][2][3]

Annabergite is an arsenate mineral consisting of a hydrous nickel arsenate, Ni3(AsO4)2·8H2O, crystallizing in the monoclinic system and isomorphous with vivianite and erythrite. Crystals are minute and capillary and rarely met with, the mineral occurring usually as soft earthy masses and encrustations. A fine apple-green colour is its characteristic feature. It was long known (since 1758) under the name nickel bloom; the name annabergite was proposed by H. J. Brooke and W H. Miller in 1852, from Annaberg in Saxony, one of the localities of the mineral. It occurs with ores of nickel, of which it is a product of alteration. A variety, from Creetown in Kirkcudbrightshire, in which a portion of the nickel is replaced by calcium, has been called dudgeonite, after P. Dudgeon, who found it.[4]

Annabergite from Lavrion (Laurium), Greece

Closely related is cabrerite wherein some of the nickel is replaced by magnesium. It is named for Sierra Cabrera in Spain where it was originally found.

References[edit]

  1. ^ Handbook of Mineralogy
  2. ^ Mindat.org
  3. ^ Webmineral data
  4. ^  One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Annabergite". Encyclopædia Britannica. 2 (11th ed.). Cambridge University Press. p. 59.