There is an excellent chart here: http://en.wikipedia.org/wiki/Albedo

That talks about the Albedo of an object, which is how much it reflects light from a light source.

There is a chart that shows all the different types of material and how they reflect light which should help with your lighting settings to get more realism.

Earths Moon which is dry and sandy has an Albedo value.

Maybe someone can create a chart for Albedo Values vs Reflective values in Carrara.