There is more silicon in the Earth’s crust than any other element except oxygen, and yet we are usually completely unaware of its presence. Whenever you pick up a rock, the chances are that silicon, along with oxygen, will make up most of it. These elements are combined as the mineral called silica. Only limestones, coals and salt beds are relatively free of silica. All sandstones, shales, and volcanic rocks contain it, as do the majority of soil particles.

We use silica to make concrete, bricks and glass, which are among the most important building materials of our world. We also use a grit of silica for “sanding” rough wooden and plastic surfaces smooth. In fact, the silicates, those minerals in which silicon is a main component, also make up some of the world’s hardest, most beautiful and sought-after minerals. Emerald and aquamarine are silicate rocks, although most of us think of them first as gems or precious stones.

In recent years scientists have found far more uses for what was, in the past, thought of as a rather unpromising element. The world’s computers and all computer controlled equipment have, at their heart, “silicon chips”, crystals of silica that are so pure that only one impure atom in a billion contaminates them beyond use.

Over one thousand different minerals have been recognised as silicates. Silicon is nearly always combined with oxygen to make the compound silica (SiO2), which is the building block of so many of the world’s minerals and rocks.

In terms of volume, silicates make up about 93% of the Earth’s crust.

Silicate compounds are not very reactive. This has the advantage of making the Earth’s surface a stable place on which to live. This is not to say that silicon makes uninteresting compounds; far from it. But nature, rather than people, is the chemist here, forming and reforming a remarkable variety of structures and giving us the beautiful minerals we see around us.