Could granite be good material for making a coin

For my chemistry extra credit, we have to create a coin and say what it would be made out of. I decided to choose granite for fun. Unfortunately, I also have to state how expensive it would be to mine it, transport it, and actually make it into a coin. Have any idea? If not, is there any other material (preferably a metal) that would be cheap?

its really common so the only really expensive thing is putting a universal symbol on it (like the head and memorial on the penny... plus since its varies in composition and thus doesnt have a exact color it would be even harder to do

i believe Aluminum is cheap

http://wiki.answers.com/Q/What_is_the_ch…

it is cheap to mine

however, each coin would have to be individually carved, instead of stamped, hampering mass production, and the coin would be brittle and break easily, wheras metals are much more difficult to break