Ottosdal is a small town situated at an altitude of 1,479 meters (4,855 feet) on the branch railway line from Makwassie in the central North West Province of South Africa.

The strata, in which it occurs, is a 3.0 to 3.1 billion year-old, over 2 kilometer-thick assemblage of arenaceous sediments, conglomerates, grits, basic volcanics, tuffs, coarse pyroclastic rocks and quartzite called the "Dominion Group".

Originally, pyrophyllite was quarried and locally used for tombstones and building stone and to carve ornaments and utensils such as pots, dishes and cases.

They include acid-resistant lab ceramics, refractory bricks and linings, filler in paint, electrical insulation, boilermaker's chalk, chromic-acid purification pots, and crucibles used in the manufacture polycrystalline-diamonds.

The quarries are also the source of naturally grooved, spherical to disk-shaped, and sometimes intergrown concretions composed of either hematite, pyrite, or wollastonite, which are collected by gem, mineral, and rock collectors and subject of much folklore.