A gemstone is a natural material that has been chosen for its attractiveness. There is no scientific reason for a material being called a gemstone.

Many gemstones form under great heat and pressure deep within the Earth. Diamonds, emeralds, rubies and beryl are like this.

Gems are stones which look very attractive and are rare. Many are hard and strong and can stand up to being cut and polished and used as jewellery.

One kind of gemstone may have several different colours. For example, opal may be black, blue, red, white or milky orange and sapphire may be blue, pink, mauve or yellow.

You can see a range of gemstones and their colours if you look at a display in a jeweller's shop.

The video below is of rubies.