Bayldonite

Bayldonite


Composition: PbCu3(AsO4)2(OH)2
Crystal System : Monoclinic
Colours: Grass-green (massive), bottle-green (crystals)
Lustre : Resinous, waxy, greasy
Hardness (H) : 4.5
Specific Gravity (S.G) : 5.24-5.65

Distribution

Common. Abundant in massive form (granular or powdery crusts) in the first oxidation zone and particularly so in the upper levels. In the second oxidation zone as rare, but well-formed crystals.

Occurrence

  • Supergene
  • 1st Oxidation Zone
  • 2nd Oxidation Zone

Notable Finds

Doubly terminated prismatic crystals with stepped faces were found in the second oxidation zone in 1973, almost certainly on 28 Level (Key, 1977). Green, twinned, tabular, pseudo-hexagonal plates of bayldonite were found in the second oxidation zone in 1980. Pseudo-rhombohedral crystal are also noted (Von Bezing et al., 2014).

Paragenetic and General Notes

Bayldonite has been reported to form pseudomorphs after the following minerals:  azurite (rare); dolomite (rare); mimetite (common); tennantite (rare); wulfenite (rare).

The following minerals have been reported to form pseudomorphs after bayldonite:  olivenite (rare).

It should be noted that a majority of "bayldonite after mimetite" pseudomorphs from the first oxidation zone turn out, on analysis, to be arsentsumebite after mimetite.