Get the diamonds by chiseling away at the rock, buy blasting kegs and jack hammer upgrades.
Ok... I made this comment a while back... but I'm not seeing it here anymore.
This game is full of bugs. Most of the time, I start out stuck in the rock on the left side of the screen. Occasionally the loading bar doesn't go away, making the game nearly impossible to play. Long stretches of the game are open screen with barely any rock on either side.
But to the actual mechanics: interesting idea, but the mining part of it and the fast running part of it don't quite gel yet. Balancing speed and amount mined would help.