Diamonds are always called a girl's best friend. They are formed from carbon and are used for a variety of purposes from jewellery to use in lasers and cutting and polishing tools. Though most diamonds are colourless you do come across a few; rare coloured diamonds.
If you've seen 'Pirates of the Caribbean', you'll have seen people fighting over rubies, pearls, diamonds and other coloured stones. What makes them so colourful and shiny, and why are they so precious?