Hemimorphite

Hemimorphite


Composition: Zn4Si2O7(OH)2.H2O
Crystal System : Orthorhombic
Colours: Colourless, white, pale-green, pale-blue, grey
Lustre : Vitreous
Hardness (H) : 5
Specific Gravity (S.G) : 3.3-3.5
References: Gebhard (1999)

Distribution

Rare. Hemimorphite occurs in both the first and second oxidation zones, and appears to have been relatively common in the outcrop and early open pit workings.

Occurrence

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

Notable Finds

At outcrop and in the upper levels, in association with hydrozincite and aurichalcite (Gebhard, 1999). Occurs in the type assemblage for reinerite, on 29 Level in the second oxidation zone (Geier and Weber, 1958).

Paragenetic and General Notes

The association of hemimorphite with aurichalcite and hydrozincite appears to have been restricted to the near-surface environment (i.e. upper portion of the first oxidation zone).  One of the earliest Tsumeb specimens in the collection of the Natural History Museum, London, obtained in 1909 (BM.1909,104), provides a fine example of this seldom-seen paragenesis.

From 29 Level, in the second oxidation zone, hemimorphite was noted as a component of the type assemblage for reinerite, accompanied by adamite, hydrozincite, olivenite, smithsonite and willemite, on a chalcocite / bornite matrix (Geier and Weber, 1958).

Hemimorphite also occurs in association with mimetite and calcite, although the level of the mine from which this paragenesis was recovered is not known (M.Southwood, personal observation).