Many chess boards are made of marble or calcite. Mexican calcite, improperly called "onyx", can have different colours. Here's an example of green/orange one : http://www.geoforum.fr/topic/15180-jeu- ... u-calcite/
I have another one that is white and yellow, and there was a pink one at the same shop.
True onyx is black and white, and is much more expensive.
If the stones and the board are both in stone, I guess that semi-convex stones are required. Biconvex stones would spin and swing after being played. And they would become worn after some time, being hit against stone repeatedly.