Andyrobertsite , Calcioandyrobertsite Locality: Tsumeb Mine (Tsumcorp Mine), Tsumeb , Otjikoto (Oshikoto) Region, Namibia ( Locality at mindat.org ) Size: 3.3 x 2.5 x 1 mm. A piece of the only known specimen of Andyrobertsite and Calcio-andyrobertsite (see the Mineralogical Record, Vol. 30, #3, May-June, 1999). The color on this single crystal ranges from a spectacular royal blue (Andyrobertsite) to a beautiful and intense green (Calcio-andyrobertsite), with a superb luster to match. Both are valid species in a series. This specimen was peeled off the TYPE SPECIMEN and so is a HOLOTYPE. This means that it is a validated piece from the type descriptive specimen listed in the scientific records for the species. It is accompanied by the label from William Pinch, who gave it to Charlie as a gift when Bill found out that he had a new species. Bill bought the specimen (said to have been found about 1950) years ago and to this day it is the only one that has turned up. This is a rare trim he peeled off it, for his friend, with documentation. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Andyrobertsite
A rare blue complex arsenate from the Tsumeb mine in Namibia, named for Geological Survey of Canada mineralogist Andrew Roberts.
Intro adapted from Wikipedia (CC BY-SA).
Andyrobertsite is an IMA-recognized mineral species in the arsenate class, with the chemical formula KCdCu₅(AsO₄)₄[As(OH)₂O₂]·2H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Andyrobertsite structural group.
Key properties: Mohs hardness 3; specific gravity 4.011; Pale blue streak; Vitreous luster; refractive index 1.742; optically biaxial.
IMA symbol Arb, IMA status: approved, named in 1997.
On a single specimen from a weathered polymetallic mineral deposit.
It is found associated with Cuprian adamite, zincian olivenite, calcioandyrobertsite, tennantite.
The mineral was named to honor Andrew C. Roberts (b. 1950), mineralogist at the Geological Survey of Canada, Ottawa.