This genus includes only one species, whose name comes from Latin and means "stone", as to point out several aspects: first of all, the triangular section and the squat shape of the leaves reminds the appearance of real stones; moreover, also the color of the plant, which when exposed to the sun, reaches grey-pink shades similar to marble; finally, even the location of its origin, often in the middle of quartz stones, makes it look like those quartz stones, perfectly blending in with them. It is also as hardy as marble, thanks to its fleshy leaves, that store water, enduring droughts and very high temperatures! Its sculptural appearance, as if a craftsman had squared geometrically perfect pieces of marble, changes in summer, when delicious yellow flowers bloom from the center of the plant, sometimes they are much bigger, than the leaves themselves! All these features make it an extremely particular succulent, a real must-have for collectors, who look for unusual shapes!