Smithsonite

Smithsonite


Composition: ZnCO3
Crystal System : Trigonal
Lustre : Vitreous, oily, pearly
Hardness : 4.0-4.5
Specific Gravity : 4.2
References: Cairncross (2010)

Occurrence

  • Supergene
  • 1st Oxidation Zone
  • 2nd Oxidation Zone
  • 3rd Oxidation Zone

Notable Finds

From the first oxidation zone white, beige-coloured, and green smithsonites were particularly abundant. Large plates of drusy green smithsonites and the epimorphic casts, or "zinkschalen" are particularly notable, and the rare parageneses in which smithsonite is associated with otavite or with tsumebite are especially desireable. In the second oxidation zone, on 28 Level for example, very aesthetic groups of modified pink rhombohedra - the classic cobaltoan smithsonites - were found (Clive King, personal communication to M.Southwood). Perhaps the best-known named pocket - the so-called "Blue Pocket" was discovered in the mid 1970s and is believed to have come from the second oxidation zone (?). In the third oxidation zone, salmon-pink and pinkish-red rhombs of "manganoan" smithsonite were discovered between 45 and 47 levels, on a matrix of massive tennantite, pyrite and germanite, and associated with crystallised chalcocite (Gebhard, 1999); apple-green smithsonites were again encountered in the third oxidation zone.