Annabergite

Arsenate mineral
(repeating unit)Ni3(AsO4)2·8H2OIMA symbolAnb[1]Strunz classification8.CE.40Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupC2/mUnit cella = 10.179(2), b = 13.309(3)
c = 4.725(1) [Å]; β = 105(1)°; Z = 2IdentificationColorApple-green, pale green, pale rose or pale pink, white, gray; may be zonedCrystal habitUsually as fibrous veinlets, crystalline crusts, or earthy; rare as well formed crystalsCleavagePerfect on {010}, indistinct on {100} and {102}TenacitySectileMohs scale hardness1.5–2.5LusterSubadamantine, pearly on cleavages, may be dull or earthyStreakPale green to whiteDiaphaneityTransparent to translucentSpecific gravity3.07Optical propertiesBiaxial (−)Refractive indexnα = 1.622 nβ = 1.658 nγ = 1.687Birefringenceδ = 0.0652V angleMeasured: 84°References[2][3][4]

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 color 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.[5]

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

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ Mindat.org
  4. ^ Webmineral data
  5. ^  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Annabergite". Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. p. 59.
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