Along with several other club members, TVJ has always been curious about the strange formation of orbicular granite. He challenged Nick Norman as to whether there was any information about this granite in his book Geological Journeys, when Nick was at the club in July. Yes, there was, and this is what it says: β€œhave a look at the famous, rare orbicular granite west of the village of Concordia. It’s a national monument, and one of just two known occurrences in South Africa, and of only a handful of such rocks around the world. The small koppie of orbicules, which are something of an enigma in geology, is quite unusual – and decorative enough to merit a visit.”

It would seem that these rocks have a unique appearance due to orbicules - concentrically layered, spheroidal structures, probably formed through nucleation around a grain in a cooling magma chamber, perhaps like very high temperature "hailstones" crystallising in successive concentric shells and eventually settling under gravity to the bottom of the chamber. Their composition often differs somewhat from the matrix surrounding them. Almost a third of all known occurrences are to be found in Finland. There are also some Archaean orbicular granitoids at Boogardie, near Mt Magnet, Western Australia. A quite technical description of the possible formation of this granite can be found at:
www.earthmuseum.see.uwa.edu.au/__data/.../orbicular_granitoids.pdf     JW