How Coloured Diamonds Are Formed

Coloured diamonds form in the same way as colourless diamonds — through the action of high pressure and temperature within the Earth's crust, in geological zones known as kimberlites or lamproites. These zones are generally located at depths of 100 to 200 km beneath the Earth's surface.

However, the presence of certain elements such as boron, nitrogen or chromium can give diamonds a specific colour. The most commonly found coloured diamonds are yellow, green, pink, blue and brown. Yellow diamonds are often caused by the presence of nitrogen, while green diamonds result from exposure to radioactive radiation. Pink and red diamonds are caused by the presence of hydrogen combined with extremely high pressure, while blue diamonds owe their colour to boron. Brown diamonds are caused by inclusions of graphite or goethite.

It is important to note that coloured diamonds are rarer than colourless diamonds and are therefore generally more expensive. Naturally coloured diamonds are also rarer than treated coloured diamonds, which is why it is important to verify the authenticity of the colour before purchasing.