Of all the oxide minerals in the Earth’s crust, silicon dioxide, or silica, is the most abundant. It is present in not only in combination with other oxide minerals but also in its isolated forms such as sand. The semi-precious mineral opal is a form of amorphous silica that has been prized for centuries.
Besides being the most abundant mineral on the Earth, it is also very important to life on our planet. Diatoms, a type of phytoplankton forming the base of the ocean’s food chain, have skeletons composed of silica. Many plants use silica to stiffen stems for holding fruit and to form external needles for protection. The role of silica is less obvious in animals, but each one of us contains about half a gram of silica – without which our bones, hair, and teeth could not be formed.
Not only does silica play an important role in biology, it had played an important role in civilization. Flint is a form of silica that was used in ancient tools.The sand used in pottery is also a form of silica. Two-thousand year-old Roman cement contains amorphous silica from volcanic ash which helps give it high strength and durability. Present technology would be very different without the silica used to create the catalysts of our oil refineries, bind the molds for casting super-alloys, form modern glass and ceramics, and polish electronic materials.