These are ‘Lithops’, members of the ice plant family. To prevent being eaten by animals, they blend into their surroundings by camouflaging themselves as pebbles or small stones!
They are tiny succulent plants which have no stem and the leaves are mostly buried in the ground; with only the top part showing on the surface to allow for photosynthesis.
They come in various shades of cream, grey and brown and the top surface is patterned with dots and lines, not even the leaves are green; making the perfect disguise to prevent being feasted on!
Oh nature -you are awesome!
For more information: http://www.lithop.supanet.com/