On another thread beekeeperswife posted a link about her BA granite which cascaded into a chain of very interesting links about kitchens and granite. It wound up on this site experimenting with etching of all "calcium-based surfaces". I really found it interesting and thought someone else might as well: http://www.granitegurus.com/2010/05/experiment-of-etching-marble-part-deux.html

Here is a link that might be useful: Experiment in marble etching