Geology of the Ciolli Quarry, Tygerberg Hills by EM Langenhoven Read the excerpt >>
An excerpt from Nick Norman's book entitled "Geology Off The Beaten Track" Read the excerpt >>

The Gran Sasso Quarry is a Malmesbury slate (Hornfels) production surface operation. The major source of stone aggregate in the mining area consists of both hornfels, a dense hard rock that occurs within the zone of thermal metamorphism close to contacts with the intrusive granites of the Cape Granite Suite and, in the Tygerberg Hills, quartzitic argillaceous sandstone of the Late Precambrian Malmesbury Group.