I have compiled a list of sources for the elements that are available to the amateur chemist. Silicon will be discussed here.
Silicon is a hard, bluish-gray semimetal. When extremely pure, it has a mirror-like shine. It is the second most abundant element in the earth's crust. It is used extensively in electronic devices. Many of its compounds exhibit typical semimetal properties; for example, the fluoride is a gas at room temperature.
In element form: Transistors and integrated circuits use silicon. Diodes contain silicon, which can be obtained by cracking the ceramic case off and breaking apart the diode via the wires.
In compound form: Silicon dioxide is found in sand and quartz. Most rocks are silicates.
This is my sample of silicon. It is one half of a cracked open diode after the wire has been cut off. The copper base is visible around the edges, while the silicon crystal is clearly seen.