I'm looking for a sample of the quartz conglomerates with the pyrite sands/pebbles from the Witwatersrand Super-group in South Africa. I need it for teaching of earth history lectures, to show the hints for less oxygenated atmosphere of the early earth (and the radiogene darkening of the quartz pebbles). Unfortunately, these rocks are hard to find at commercial mineral and rock shows, so I want to ask if somebody has a "left-over"-sample for me from his/her personal collection or can provide me a hint, who I may ask for for such a sample.
With best regards
Johannes