Go to The State Building located at Post Code 506 and apply for the mining job. From there you can go to the Davis Quartz Quarry where you will be issued a pickaxe or Drill (Jackhammer), then LOOK at the ground and the rocks in the area and mine away. After gathering dirty rocks you will need to clean them before taking them to have them smelted. You will have to locate where you need to washing the stones.

After washing stones you will have to take them to be smelted which will reveal your findings. At that point you have options, you can sell them to Jorge located just a short walk away. But beware, Jorge has been known to lowball the price. You can look for other buyers who might give you a better deal.

The second location is a C4 Blasting area which you can locate on the map. There you will need to be extra careful as you will use explosives to crumble the rock, which will tneed to be washed using the process above. You will need to find Sam to purchase the C4 and follow his requirements. Locate a blasting site, as there are several spread out for safety reasons. Stay far away from the blast to prevent injury then go and to gather the stones.