Question 1

Why are natural blue diamonds so rare?

Accepted Answer

Blue colour in most natural blue diamonds requires boron, and the element is scarce in the deep earth where diamonds form. The diamond must also contain almost no nitrogen, which is unusual. Only a handful of mines have produced blue diamonds in commercial quantities, and strongly coloured stones remain a very small fraction of that output.

Question 2

What does greyish blue mean on a report?

Accepted Answer

Greyish blue means the diamond's colour is predominantly blue with a grey modifier. Grey is common in natural blue diamonds and softens the colour, making it appear less vivid. Greyish blue stones are generally priced below pure blue diamonds of the same intensity grade, although they can still be attractive and are much more available.

Question 3

Can a lab tell if a blue diamond is treated or lab-grown?

Accepted Answer

Major laboratories such as GIA use spectroscopy and other advanced methods to identify irradiated, coated and lab-grown blue diamonds, and their reports state whether the colour origin is natural. Simple testers cannot reliably do this. Because HPHT-grown blue diamonds also conduct electricity, conductivity alone does not prove a natural stone.

Question 4

Where do blue diamonds come from?

Accepted Answer

The Cullinan mine in South Africa has been the most important modern source of natural Type IIb blue diamonds. Historic blue diamonds, including the Hope diamond, are believed to have come from India. Other mines have produced occasional blues, and Argyle in Australia produced blue to violet stones with a different cause of colour.

Natural Blue Diamonds