Glaucodot

(Co,Fe)AsS (Co0.75Fe2+0.25AsS)IMA symbolGl[1]Strunz classification2.EB.10cCrystal systemOrthorhombicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP21/cIdentificationFormula mass165.15 g/molColorGrayish tin white, Reddish silver whiteCrystal habitMassive , prismatic habits with elongated sphenoids, granular masses- Uniformly indistinguishable crystals forming large masses.CleavageNoneFractureBrittle - Uneven - Very brittle fracture producing uneven fragments.Mohs scale hardness5LusterMetallicStreakblackDiaphaneityOpaqueSpecific gravity5.9 - 6.01, Average = 5.95Ultraviolet fluorescenceinertOther characteristicsNonmagnetic, non-radioactive

Glaucodot is a cobalt iron arsenic sulfide mineral with formula (Co,Fe)AsS. The cobalt:iron(II) ratio is typically 3:1 with minor nickel substituting. It forms a series with arsenopyrite (FeAsS). It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the orthorhombic system. The locality at Håkansboda, Sweden has rare twinned dipyramidal crystals (see photo). It is brittle with a Mohs hardness of 5 and a specific gravity of 5.95. It occurs in high temperature hydrothermal deposits with pyrrhotite and chalcopyrite. Glaucodot is classed as a sulfide in the arsenopyrite löllingite group.

Glaucodot was first described in 1849 in Huasco, Valparaíso Province, Chile. Its name originates from the Greek Ancient Greek: γλανκός ("blue") in reference to its use in the dark blue glass called smalt.

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.
  • Webmineral:Glaucodot
  • Mindat with location data
  • Scandinavian mineral gallery Archived 2008-11-20 at the Wayback Machine
  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., p. 288, ISBN 0-471-80580-7
Wikimedia Commons has media related to Glaucodot.


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