Information:

Travertine   Also known as Travertin and Calc-sinter.
Stalagmatic bed, produced by deposits of carbonate of lime, petrified over the course of centuries.
Used in block-form as a building material for floors, walls etc. dating back to Ancient Rome.

The painted imitation of rock, granite and marble is taught at various places throughout the world.
See:   http://www.painting-effects.co.uk/workshops.htm