What does sand make of?

As quoted from http://en.wikipedia.org/wiki/Sand.

"The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide), usually in the form of quartz.

However, the composition of sand varies according to local rock sources and conditions.

The bright white sands found in tropical and subtropical coastal settings are ground-up limestone.

Arkose is a sand or sandstone with considerable feldspar content which is derived from the weathering and erosion of a (usually nearby) granite. Some locations have sands that contain magnetite, chlorite, glauconite or gypsum.

As a whole, sand is a compound of silicon dioxide and other metal oxides, carbonate, sulphate, etc.