The agates are eroded from the gravels transported and deposited by the Caledon River. The gravel also contains other gemstones and diamonds and occurs in a vast area along the present Caledon River. Two different types of agates are found together although they are believed to originate from different areas. The origin of the agates is unknown.
Blue grey agates: Mostly fragments, full agates are usually small to very small. Blue grey and translucent outer skin, smooth, finely pitted sandpaper look to coarse. Black and white and grey bands in translucent chalcedony. Chatoyance is very common. Widespread on the farms along the Caledon River. Size up to 60 mm.
Brown agates: Brown rather smooth outer skin with sharp white to grey bands in translucent chalcedony. The finer bands display chatoyancy. These agates seem to be deposited in a gravel layer about 2 metres below the surface and are only found eroded on the sides of outcrops or during new excavation. Size up to 110 mm.
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