rocks, gravel & sand

Ever wonder how sand is made? I was out and about today with John and we made a stop by the rock, gravel & sand place (I'm calling it that because I don't remember the real name). They take huge pieces of rock, grind them in these enormous (at least 3-story) machines to get smaller rock. They grind them again to get gravel, grind them again to get sand. Sometimes they even mix the small gravel & sand together. CPC uses all of these mediums for a house (whether in the foundation, stucco, cement, and who knows what else). I've driven by the place countless times & just thought it was a big dustbowl. Now I know!