Natural Stone is available in many forms and finishes, with porous ones providing the best adhesion. Before using, always make sure the stone is thoroughly cleaned.
It is generally fine to draw or paint directly on clean stones with acrylics, oils, and watercolors. If less absorbency is desired, apply a commercial masonry primer or conditioner, or else a thin acrylic medium such as GAC 100 or Fluid Matte Medium, as a base coat.
For added protection, a suitable topcoat or varnish can be used as well.