Quartz

Quartz


Composition: SiO2
Crystal System : Trigonal
Colours: Colourless, milky-white, cream, grey, brown, red, yellow
Lustre : Vitreous, slightly greasy
Hardness (H) : 7
Specific Gravity (S.G) : 2.66

  

Distribution

Very common. Occurs in varying amounts throughout much of the Tsumeb deposit.

Occurrence

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

Notable Finds

A remarkable 70 mm terminated quartz crystal, overgrown by a druse of carbonate was recovered from 13 Level (at the base of the first oxidation zone) and is the Wilhelm Klein collection at Harvard University (Klein # 127336; Harvard University # 127336).

Paragenetic and General Notes

Quartz is a common mineral at Tsumeb, and abundant in parts of the deposit.

Notably, from 26 Level downwards (i.e. from below the top of the second oxidation zone), silicification is an important alteration style associated with the hypogene mineralisation. Furthermore, quartz is an essential component of the feldspathic sandstone ("pseudo-aplite").

Well-crystallised quartz of specimen quality, however, is relatively scarce.

Pinch and Wilson (1977) report that colourless, grey and milky crystals to 10 mm have been found. Quartz "points", typically colourless, prismatic crystals with clear pyramidal terminations, to 2 or 3 mm, are quite commonly encountered with a wide variety of associated minerals.

Red quartz crystals, due to the presence of cuprite inclusions are notable (Von Bezing et al., 2014).

Quartz has been reported to form pseudomorphs after the following minerals:  azurite (rare).

Coatings of drusy, colourless quartz, presumably of authigenic origin, were commonly observed in the upper parts of the first oxidation zone, encrusting secondary mineral species and assemblages.