You can recognise a crystal by its flat sides. Where the sides meet they may make sharp corners or even points. Some crystals let light through them. Many crystals are colourless or white. Others are coloured.

We tend to think of crystals as sparkling, almost magical objects. It is true that the crystals of minerals may be found this way, but crystals can also be found in the home. Salt and sugar are two common substances that are made of crystals. Look at them with a magnifying glass to see their crystal shapes.

Other materials are made of crystals. For example rocks such as granite are made of crystals that are locked together. All metals are made of crystals, although most of the crystals are too small to see. You can, however, sometimes see the crystals of zinc when it is used as a weatherproof coating called galvanising. This is a metal that is used to coat farm gates, for example. The pattern on the zinc is made by the edges of the crystals.