Blue diamonds are amongst the rarest of all the fancy coloured diamonds. These beautiful stones can vary from a light to deep blue, and have grey or green secondary tones. Natural blue diamonds are a rarity in nature, and are the only type of diamond that can conduct electricity! It goes without saying that a blue diamond would look spectacular in an engagement ring. Find out more about these captivating diamonds here.
Blue diamonds gain their colour from the trace element boron. When single boron atoms replace carbon atoms in the diamond’s structure, a blue colour is formed. These examples contain no other impurities, and as such have exceptional clarity. Blue diamonds with a high colour intensity are amongst the rarest of all the coloured diamonds, second only to red diamonds.
As mentioned above, blue diamonds can possess a green or grey secondary tone. These secondary colours are a result of unique growing conditions for the diamond crystals. Some blue colours can be caused by radiation exposure whilst the crystal was forming. Diamonds that have been exposed to this are often called ‘greenish blue.’ Hydrogen can also be present within the diamond’s crystal structure and this causes a ‘greyish blue’ colour.
One of the most famous diamonds of all time was a blue diamond. The Hope Diamond weighed 45.52ct and was assessed as fancy dark greyish blue. It was stolen from the French Crown Jewels during the revolution in the 18th century. It was subsequently recut, and purchased by Henry Philip Hope in 1830. The stone acquired its name from this famous collector and is currently on display at the Smithsonian Natural History Museum in Washington.
Historically, blue diamonds have been associated with the Golconda mines of India. However, blue diamonds have also been sourced from the Cullinan mine in South Africa.
Over the last century, scientists have developed combination treatments to turn diamonds blue. These HPHT treated diamonds do not have a natural colour origin, and are nowhere near as highly sought-after as their natural counterparts. We would recommend sourcing any fancy coloured diamonds from a trusted and knowledgeable source to avoid unwittingly purchasing a lower value treated blue diamond.