Richelsdorfite

richelsdorfite

duftite

tyrolite

tetrahedrite

Images

Formula: Ca2Cu5Sb5+(AsO4)4(OH)6Cl.6H2O
Hydrated arsenate containing halogen
Specific gravity: 3.2 to 3.3
Hardness: 2
Streak: Greenish blue
Colour: Turquoise-blue
Solubility: Readily soluble in 1:10 hydrochloric acid
Environments

Sedimentary environments
Hydrothermal environments

Localities

At Triembach-au-Val, Sélestat-Erstein, Bas-Rhin, Grand Est, France, richelsdorfite is associated with erythrite, chalcophyllite, cornwallite, strashimirite, tetrahedritetennantite and baryte (HOM).

At the type locality, the Wilhelm mine, Nentershausen, Hersfeld-Rotenburg, Kassel Region, Hesse, Germany, richelsdorfite was found in sandstone, associated with calcite, duftite, tyrolite and tetrahedrite, later it was also found in cavities in baryte and as an incrustation on blocks of copper shale. Richelsdorfite occurs mostly in very small speheroidal aggregates up to 0.2 mm in diameter; rarely, tabular single crystals may attain 0.5 mm in size (AM 69.211).

At the Samson Mine, St Andreasberg, Braunlage, Goslar District, Lower Saxony, Germany, richelsdorfite was found in cavities in quartz with calcite, tetrahedrite, galena, brochantite and devilline (AM 69.211).

At the Dolyhir Quarry, Old Radnor, Powys, Wales, UK, thin calcite-filled fractures in limestone adjacent to the lead-copper vein contained abundant tennantite-(Zn), with baryte, chalcopyrite, enargite, galena and minor relict sphalerite. The top of the vein exposure was very close to the original land surface and oxidation had produced a diverse assemblage of secondary minerals including azurite, copper, cuprite, malachite, mimetite, tyrolite and zincolivenite.
Turquoise to sky-blue crystal aggregates of richelsdorfite were found on a small number of specimens.
The copper and arsenate ions required for the supergene minerals to form are likely to have been released by the oxidation of tennantite-(Zn). Calcium was almost certainly supplied by calcite, which is ubiquitous in the fractures and surrounding limestone. The antimony required for richelsdorfite was probably also supplied by tennantite-(Zn) as no other antimony-bearing primary phases are present. There is sporadic substitution of antimony for arsenic in tennantite-(Zn) from the main vein and surrounding calcite-rich fractures (JRS 23.33-38).

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