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
IMA symbol Arb [1]
Strunz classification 8.DH.50 08
Dana classification42.09.02.03
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
ColorBlue
Crystal habit Platy
Cleavage {100} good
Mohs scale hardness3
Luster Vitreous
Streak Pale blue
Diaphaneity Transparent
Specific gravity 4
Optical propertiesBiaxial (-)
Refractive index nα = 1.72, nβ = 1.749, nγ = 1.757
Birefringence δ = 0.037
References [2] [3]

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. [3]

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2
,Na
2
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Si
4
O
12
•6H
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. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.

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<span class="mw-page-title-main">Paragonite</span>

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3
(PO
4
)
2
(OH)
5
·H
2
O
. Crandallite was named after Milan L. Crandall, Jr, who worked for Knight Syndicate. This mineral is found in laterite and in alteration products of phosphate rich pegmatites.

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. Andyrobertsite. Mindat.org
  3. 1 2 Andyrobertsite. Webmineral.com