Split stone succulents

Lithops thrive best in a coarse, well-drained substrate. Any soil that retains too much water will cause the plants to burst their skins as they over-expand. Plants grown in strong light will develop hard strongly coloured skins which are resistant to damage and rot, although persistent overwatering will still be fatal. Excessive heat will kill potted plants as they cannot cool themselves by transpiration and rely on staying buried in cool soil below the surface.
Lithops occur naturally across wide areas of Namibia and South Africa, as well as small bordering areas in Botswana and possibly Angola, from sea level to high mountains. I got these at Home Depot.