Glaucodot Locality: Håkansboda, Lindesberg , Västmanland , Sweden ( Locality at mindat.org ) Size: 3.3 x 2.7 x 2.6 cm. A remarkable and LARGE, 40-gram crystal of this rare complex iron-cobalt sulfide. It is complete all around except for a contact on the bottom and one small contact or old damage in a 7 x 5 mm edge on one face. It is geometric and very 3-dimensional, displayable from 3 sides thus. Ex. Phillipstad Museum Collection in Sweden (over 50 years ago). — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Glaucodot
A cobalt-iron arsenic sulfide in series with arsenopyrite — an ore accessory named for its gray-blue tint.
Intro adapted from Wikipedia (CC BY-SA).
Glaucodot is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula (Co₀.₅Fe₀.₅)AsS.
It crystallizes in the orthorhombic crystal system (space group Pn2_1m). It is a member of the Arsenopyrite structural group.
Key properties: Mohs hardness 5; specific gravity 6.055; Black streak; Metallic luster.
IMA symbol Gl, grandfathered status — known before the IMA’s founding, named in 1849.
Found in deep-seated deposits of high-temperature hydrothermal origin.
It is found associated with Cobaltite, pyrite, chalcopyrite.
Its name comes from the Greek for blue, in reference to its use in the dark blue glass called smalt.