The native habitat of these plants is South Africa and Namibia. Since they resemble small pebbles, they are commonly known as living stones. Each plant consists of two thick, fleshy leaves separated by a narrow fissure in the center. Depending on their environment, the leaves can range in color from gray-green to brown. Their shapes are cylindrical, with upper surfaces that are smooth—either flat or slightly domed. On the upper surfaces, there are darker markings or round spots. Through the thin, window-like areas between these darker spots, the plant receives the light needed for photosynthesis.