Aragonite

Aragonite


Composition: CaCO3
Crystal System : Orthorhombic
Colours: Colourless, white, cream, pale-yellow, pale-green, blue
Lustre : Vitreous, resinous
Hardness (H) : 3.5-4.0
Specific Gravity (S.G) : 2.947

Distribution

Common. First, second and probably (?) third oxidation zones.

Occurrence

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

Notable Finds

Fine specimens of the lead-bearing variety "tarnowitzite", and the zinc-bearing "nicholsonite" were recovered from the first oxidation zone. Numerous specimens of pale-blue copper-bearing aragonite, commonly as sub-botryoidal crusts, are of post-mining origin.

Paragenetic and General Notes

Relatively pure aragonite forms slightly greenish to bluish needles and turquoise-coloured masses and crusts; it occurs only rarely as dull, prismatic, pseudo-hexagonal crystals, and is far more scarce than calcite (Pinch and Wilson, 1977).

Much more common than "pure" aragonite is the lead-bearing variety "tarnowitzite", which forms excellent cream-white prismatic crystals to to several centimetres, terminated by pseudohexagonal pyramids. The zinc-bearing variety "nicholsonite" also forms similar excellent crystals, typically buff-cream or very pale blue-green in colour.

The following minerals have been reported to form pseudomorphs after aragonite: malachite (rare); smithsonite (rare).