Huge agates originating from ancient eroded basalt are found in the Maputaland Midlands. Most known locations are reported exhausted and no new ones discovered for the last 25 years.
Outside rough skin agates, dark or translucent exterior. Inside uniform grey to dark grey chalcedony with some bright colour inclusions or some horizontal banded layers in soft grey or pink and sometimes red. The huge agates are sought after and presently very scarce.
More informations about this material and other southafrican gemstones are offered at the homepage of afrigemtec