Andyrobertsite

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Andyrobertsite
Andyrobertsite-Calcioandyrobertsite-117541.jpg
A mixture of andyrobertsite (blue) and calcioandyrobertsite (green), holotype specimen; size: 3.3×2.2×1.0 mm
General
Category Arsenate mineral
Formula
(repeating unit)
KCdCu5(AsO4)4(H2AsO4)·2H2O
Strunz classification 8.DH.50 08
Dana classification 42.09.02.03
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/m
Unit cell a = 9.81, b = 10.034
c = 9.975 [Å]; β = 101.83°; Z = 2
Identification
Color Blue
Crystal habit Platy
Cleavage {100} good
Mohs scale hardness 3
Luster Vitreous
Streak Pale blue
Diaphaneity Transparent
Specific gravity 4
Optical properties Biaxial (-)
Refractive index nα = 1.72, nβ = 1.749, nγ = 1.757
Birefringence δ = 0.037
References [1][2]

Andyrobertsite is a rare, complex arsenate mineral with a blue color. It is found in the Tsumeb mine in Namibia and named after Andrew C. Roberts (b. 1950), mineralogist with the Geological Survey of Canada. A Ca-rich analogue (with Ca instead of Cd) is called calcioandyrobertsite and has a more greenish tint.[2]

References[edit]

  1. ^ Andyrobertsite. Mindat.org
  2. ^ a b Andyrobertsite. Webmineral.com