McP77

[quote=Gaz @ Topps;22010]Limestone,Travertine and Marble are all calcium carbonate,and very closely related CaCO3,very difficult to make a clear defenition between them, thanks McP77:wink_smile:[/quote]

You're not wrong there. I've looked into it a bit more and it's quite interesting. Apparently pure travertine is white and the colours come from impurities. Travertine is formed when carbon dioxide rich water goes through limestone and disolves the limestone. When this water resurfaces later the change in pressure and temperature causes the water to release the carbon dioxide and then recrystallises.

(sorry if this thread is getting geeky, I'm a closet wannabe)