The blue color in Azurite
is much sought after by collectors. It has been used as a stain for
centuries. It is sometimes replaced by malachite to form interesting psuedomorphs.
The mineral azurite, the basic carbonate of
copper, is used as a decorative stone and a blue pigment. Azurite
occurs in the oxidized zone of copper deposits, where it has been
precipitated from low-temperature copper and carbonate-rich
solutions. It is almost always associated with the more abundant
green copper carbonate malachite, to which azurite weathers. It forms
modified monoclinic crystals as well as columnar or earthy masses
that have a vitreous luster and a distinctive azure-blue color.
Azurite in Tsumeb
The richest pockets of azurites were found in
the eighties at Tsumeb. Crystals were found at the upper zones in the
oxidation zone.
The largest crystals recorded from Tsumeb as
from anywhere have reached 50 cm in length, but these crystals were
dull. They have rough surfaces, mostly altered to malachite. The
exception was a large crystal that was at the Newmont mining office
for a long time. This specimen had crystals up to 15 cm with some
partly altered to malachite. But this specimen had an interesting
history. A miner had to leave it at the bar in Tsumeb because he
could not pay for his beer. It was worth more than a thousand times
than what the bill was for the beer!
Some of the finest azurites known originally
belonged to the collections of the mine manager, F W Kegel and his
mine Captain ,Wilhelm Klein. These specimens are now in the
collections of the Smithsonian and Harvard. All these specimens came
from the 8th level. Other superb specimens were sold by the miners
after the Second World war in Germany.
A classic story of an azurite find is the one
of the Easter pocket in 1994. On the eighth level a shift boss saw
tell tale signs of a possible pocket after a blast. After taking away
the rubble he opened a pocket of first class azurites. A pocket of 80
cm by 2 meters were lined with azurites. The entrance to this vug was
lined with malachite. On the sides of the pocket the crystals started
at a few millimeters and increased deeper into the vug to some 5 cm
crystals. Only at the end of the pocket was the crystals attached to
matrix. The major part of the inner pocket consisted of floaters of
near perfect azurites. .
