Azurite, (w. Malachite)

Azurite


Composition: Cu3(CO3)2(OH)2
Crystal System : Monoclinic
Colours: Blue, blue-black
Lustre : Vitreous, sub-adamantine
Hardness (H) : 3.5-4.0
Specific Gravity (S.G) : 3.77

Distribution

Very common. Abundant throughout the first oxidation zone. One or two significant finds in the second oxidation zone.

Occurrence

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

Notable Finds

There were many significant finds of azurite, of which the following named pockets stand out: The Gordon/Kegel pocket on 8 Level (1929); the Easter Pocket on 8 Level (1994); and the Perkins Sams Pocket (probably from the NW stope, Number 2 sub-level, on Level 35) in late 1980.

Paragenetic and General Notes

As fine lustrous, blue-black crystals to 25 cm; poorly developed crystals to 50 cm have been reported. Many are more or less altered to malachite. The vast majority of azurite is from the first oxidation zone but one or two important pockets were recovered from the second oxidation zone.

Keller (1977) places azurite as an important component of his "Type I" parageneses (i.e. minerals forming at relatively higher pH values). However, he notes that azurite also occurs with minerals that are typical of Type II parageneses, and cites that observation as evidence that oxidising solutions evolved from acidic to basic. Keller identified the following parageneses involving azurite:

(1) duftite >> dundasite >> cerussite >> azurite >> malachite (ps. azurite).

(2) quartz >> mottramite >> olivenite >> duftite >> malachite >> azurite >> malachite (ps. azurite).

Azurite does not, as a rule, appear to replace other minerals.  However, a remarkable specimen in the Folch Collection appears to consist of an encrustation pseudomorph of azurite after a cerussite "sixling" (Carl Acosta and Jordi Fabre, personal communications to M.Southwood, 2015).

The following minerals have been reported as forming pseudomorphs after azurite:  arsentsumebite (rare); aurichalcite (rare); bayldonite (rare); brochantite (rare); chrysocolla (rare); dolomite (rare); duftite (rare); enargite (rare); jarosite (rare); malachite (abundant); plancheite (rare); quartz (rare); rosasite (rare); smithsonite (rare); tennantite (common).