The word quartz comes from the ancient German word for 'hard'. Quartz is a very common mineral that often makes spectacular crystals. It is made of the elements silicon and oxygen (so it is made of silica). It is is the second most common mineral in the Earth's surface rocks (feldspar is the first).

Because some impurities often get inside the quartz structure, there are many variations of quartz, and some are shown in the videos below. Some are used in jewellery. Citrine and amethyst are varieties of quartz.

The crystals of quartz have six sides and often have a pointed top. It has a hardness of 7 and is therefore a bit harder than steel.

Most sand grains are quartz because it is hard and resists wearing away. If they look yellowish, that is because they have impurities of iron in them.

You can see quartz crystals in granite. It makes up the transparent minerals. (The white or pink crystals are feldspar).