Calcite

Calcite


Composition: CaCO3
Crystal System : Trigonal
Colours: Colourless, white, grey, cream, pale-green, pink, orange, red
Lustre : Vitreous
Hardness (H) : 3
Specific Gravity (S.G) : 2.71

Distribution

Abundant, and widespread throughout the Tsumeb deposit.

Occurrence

  • Hypogene
  • Supergene
  • Country Rock
  • 1st Oxidation Zone
  • 2nd Oxidation Zone
  • 3rd Oxidation Zone

Paragenetic and General Notes

Calcite is almost ubiquitous at Tsumeb, occurring as a component of the host-rocks, as an alteration product of (hypogene) mineralisation (calcitisation), and as the result of (supergene) oxidation processes in the secondary mineral assemblage. The latter process has generated a vast variety of habits, colours and associations, with crystals up to 200 mm. Gebhard (1999) notes that "Calcite is the most common mineral at Tsumeb and is associated with nearly all other minerals." Rhombohedral crystals are very common, while scalenohedral forms are relatively rare.

Calcite has been reported to form pseudomorphs after the following minerals: cerussite (rare); mimetite (rare).

The following minerals have been reported to form pseudomorphs after calcite:  conichalcite (rare); descloizite (rare, doubtful status); dolomite (common, often as epimorphs); galena (rare); mottramite (rare); smithsonite (rare, doubtful status).