I really like this quote "DIAMONDS" in the ruff
Over 100 mineral species have been reported from the gold-bearing reefs. Most of the minerals are esoteric and visible only under the microscope and seldom form larger collector specimens. Zircon, chromite and other "heavy minerals" occur throughout the Witwatersrand. The most common silicate minerals in the reefs are quartz, muscovite, pyrophyllite, chloritoid and chlorite. The sulphide minerals are the second most abundant minerals superceded only in volume by quartz. A wide variety of nickel-cobalt-platinum sulpharsenides as well as copper sulphosalts ans antimony-bearing minerals are present. Included in this group are speciessuch as cobalt-rich arsenopyrite, gersdorrite and cobaltite, and the platinum group minerals geversite, sperrylite, braggite and cooperite. Pyrite is present in a variety of habits and forms. The main uranium-bearing minerals are uraninite and brannerite with minor amounts of coffinite and uanothorite. Uranium (and gold) tends to be enriched when found in combination with carbon. In some places a "reef", the Carbon Leader, is developed and mined as the gold content is exceptionally high.3
Diamonds are also assiciated with the Wtwatersrand reefs (some diamonds up to 8 carats where found). There failure however was there green colouration ranging from a nuance of green to bottle green and almost black. This colour it was found to be the result of the natural radiation caused with the association of uranium. Diamonds are however no longer recovered from the Witratersrand gold mines due to a change in the reduction procedure. Most of the gold in the Witwatersrand is present as native gold which occures in a variety of formes and habits, such as microscopic veinlets or overgowths and is usually only visible under the microscope (the average gold particle ranges from 0.005mm to 0.5mm in diameter). There are however remarkable exceptions. On the Randfontein Estates gold mine, gold was found in an area where a dolerite dyke had transgressed the strata and the gold was found "smeared into" the fault planes. Spectacular finds of native gold were also found in the City Deep Mine. One of these finds comprised of a interwoven gold crystals which formed small mats found between the walls of a fissure (associated with a dolerite sill) in the Main Reef Leader. Close to the fissure 15-20cm rhombohedral calcite crytals where found. In this mine beautiful clear quartz crystals up to 10cm long with small calcite crystals were found.4 |
