There are a wide range of gemstones used in jewellery, with each having its own characteristic colour – or, in some cases, a range of colours.

The origin of these colours has a chemical basis, and the precise colour can vary depending on the chemical composition of the gemstone. Interestingly, many minerals are actually colourless in their pure form, and it is the inclusion of impurities in their structure which leads to their colouration.

Generally speaking, we observe an object as coloured when it absorbs some wavelengths of visible light, but not others. Different colours of light have different wavelengths, so the exact wavelengths that are absorbed will affect the colour that the object appears. For example, an object that absorbs all wavelengths of visible light that pass through it, but does not absorb red light, will appear red.