Fancy Blue

Blue is the cool exception in a family that runs mostly warm. Its colour comes from boron, an element that enters the lattice in place of carbon and absorbs light at the red end of the spectrum, leaving the deep blue we see. Boron makes a blue diamond Type IIb — and gives it a property no other diamond shares.

The trait that cannot be faked

The boron that colours a blue diamond also makes the stone semi-conductive — it carries a faint electrical charge, where every other diamond is an insulator. This is more than a curiosity. It is a signature of natural origin: irradiation and other treatments can mimic a blue hue, but they cannot reproduce the semi-conductivity that boron confers. The stone’s own physics testifies to how it was made.

A spectrum of blues

Natural blues range from a pure, saturated blue toward stones carrying greenish or greyish hints, the hue shifting with the concentration of boron and the way the crystal grew. As with every fancy, it is intensity that governs value — a deep, clean blue of strong saturation is among the most coveted colours a diamond can take.

The most famous of them all

No blue diamond is more storied than the Hope Diamond — the deep blue stone whose history and mystique have made it the most famous coloured diamond in the world, and a benchmark by which all blues are imagined. Stones of that order are extraordinarily rare; natural blue is one of the scarcest fancy colours to occur at all.