Silicon is a chemical element, one of the 97 natural building blocks from which our minerals are formed. A chemical element is a substance that can not be subdivided into simple substances without splitting atoms. Silicon is the second most abundant element in the earth s crust, making up about 27% of the average rock. Silicon links up with oxygen (which makes up 55% of the earth s crust) to form the most common suite of minerals, called the silicates. Quartz, feldspars, olivine, micas, thomsonite, jadeite, and prehnite are all silicates. There is so much oxygen around that pure native silicon is almost never found naturally.