This is a video showing a nice animation of how semiconductor wafers are produced.  This process is called wafering, and it starts with refining sand (quartzite) into electronic grade polysilicon material (EGS). This EGS material is then used to grow single-crystal near-perfect cylindrical silicon ingots. These ingots are then ground and sawn into the thin and round silicon wafers familiar to us.  The wafers are then polished prior to being used as substrate for IC fabrication.