A mass of limestone of the lower Paleozoic Sicamous Formation (Mount Ida Group) extends northwest from the community of Grindrod for 6.4 kilometres. The mass varies up to 2.5 kilometres in width. The body is truncated by a fault along its northeast margin and intruded by a Cretaceous? granitic stock along its southwest flank.

Outcrops along the Grindrod-Mara road reveal siliceous limestone with quartz veins and granitic dikes. A cut along a side road on a hill, 1.6 kilometres west of Grindrod, exposes platy, orange and black limestone with mica and graphite along partings. A sample taken along 12 metres of this exposure analysew 47.53 per cent CaO, 0.57 per cent MgO, 11.80 per cent insolubles, 1.28 per cent R2O3, 1.22 per cent Fe2O3, 0.04 per cent MnO, 0.03 per cent P2O5, 0.09 per cent sulphur, 38.72 per cent ignition loss and 0.24 per cent water. (Minister of Mines Annual Report 1960, page 144, sample 2).