The element Silicon (Si) is not a mineral, since it does not occur in nature. Sililica's most common form is SiO2, or silica dioxide. Silica dioxide is a mineral. This is quartz or common sand's basic constituent. Silicon is produced by heating sand (SiO2) with carbon to temperatures around 2200°C. At room temperatures, silicon exists in two forms, amorphous and crystalline. Amorphous appears as a brown powder while crystalline silicon has a metallic luster and a grayish color. The silicon in the photo is crystalline silicon. Silicon is used in the manufacture of transistors, solar cells, rectifiers and microchips. Silicon dioxide (SiO2), silicon's most common compound, is the most abundant compound in the earth's crust, and comprises roughly 14% of the earth's crust. SiO2 is mined both as sand and as vein or lode deposits, for use in industry. Another example of an element that we could not live without, in the modern world. Some information provided by USGS