This small stone-like and soft-skinned mesemb used to be called Pleiospilos hilmarii. It grows naturally in the Western and Northern Cape provinces. The chunky mesemb leaf pairs may be green or have a reddish or purple hue, with distinctive mottling all over the leaf surfaces. 

The plant produces spectacular yellow vygie-like flowers in spring and is cultivated in many countries from seed (www.cactus-art.biz).