Silicon and oxygen are two of the most common elements on Earth. Together, they make up nearly 75 percent of the Earth's crust, so it is no surprise that they play major roles in forming many of the minerals that we see in rocks. The silicon atom, which has four electrons in its outermost region, likes to form chemical bonds with oxygen atoms, which are attracted to extra electrons. Thus, silicon and oxygen, together with some of the metallic elements, can combine to make hundreds of different minerals. For example, quartz has two oxygen atoms for every silicon atom, and feldspar has two or three silicon atoms grouped with eight oxygen atoms and a few metal atoms. About half of the most common minerals found on Earth belong to the silicate group, as do some beautiful gemstones such as amethyst, opal, and topaz.

Since antiquity, humans have made pottery from clay, which consists of fine particles of silicate minerals. Kaolinite is an aluminum silicate mineral, and it is the main component of porcelain, a particularly hard type of ceramic. Clay, which is used to make other types of pottery, may contain silica and grains from sedimentary rocks. Quartz, also referred to as silica or silicon dioxide, is a key component of another important solid material: glass. In the ancient Middle East, humans made glass by heating silica with alkali that was made from the ashes of plants. Other minerals such as calcium, lead, calcium, and manganese were added to improve the glass. Metals and metallic oxides were also added to color the glass or to make it clear, since natural glass tends to be slightly colored from impurities in the sand. Ruby red is made from powdered gold, while an orangey-red is produced by copper oxides. If the glass with copper oxide is heated too much, it will turn green. Cobalt and iron can make blue glass, and manganese is used for purple. Antimony or manganese oxide will produce clear glass. Glass for specialized purposes, like cookware and optical instruments, may require additives, such as boron oxide or lead oxide.