Chalcosiderite Locality: Cornwall , England , UK ( Locality at mindat.org ) Size: 6.8 x 6.1 x 4.8 cm his is a beautiful chalcosiderite specimen, with an intense sparkle and glistening surface, as the thousands of small crystals drape a 3-dimensional matrix plate. The heyday of the mining here was in the mid to late 1800s. From the collection of E.R. Chadbourn, (1855-1920s). See Min Record archives here: http://www.minrec.org/labels.asp?colid=1289 . — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Chalcosiderite
Chalcosiderite is an IMA-recognized mineral species in the phosphate class, with the chemical formula CuFe³⁺₆(PO₄)₄(OH)₈·4H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Turquoise structural group.
Key properties: Mohs hardness 4.5; specific gravity 3.22; White to greenish, pale green streak; Vitreous luster; optically biaxial.
IMA symbol Csd, grandfathered status — known before the IMA’s founding, named in 1814.
A rare mineral found in the oxidized zone of some hydrothermal mineral deposits.
It is found associated with Dufrénite, goethite (West Phoenix mine, Cornwall, England); dufrénite, cyrilovite, leucophosphite (Gunheath china clay pit, Cornwall, England); sampleite.
Its name comes from the Greek for copper and iron, for those elements in the mineral’s composition.