Boron - A Girl's Best Friend's best friend

What is a girl's best friend? A "fancy, vivid" diamond, of course and there's a Bulgari Blue two stone diamond ring going up for auction at Christie's this week. It contains a spectacular blue diamond and is expected to fetch $12 to $15 million.

What makes this diamond so valuable?
Boron. On a submicro scale, pure diamond is billions of billions of carbon atoms bonded to one another. If you shrunk yourself down and stood inside the diamond, you'd see nothing but carbon in a perfect pattern in every direction.

Carbon atoms have four electrons available to form bonds with four other atoms, and because there's nothing else but carbon to bond with inside a diamond, each of the four bonds is equally strong, leaving no weak spots in any direction. This gives diamonds their proverbial hardness, but also leaves them transparent.

Light interacts primarily with electrons, and when all the electrons are tied up in bonds, visible light streams right through.

The Hope Diamond at the Smithsonian's Instutute

Periodic table
Boron is carbon's neighbour on the periodic table, which means it can do a passable carbon impression and wriggle its way into the matrix of a diamond but it has one fewer electron, so it can't quite form the same four perfect bonds.

This different distribution of electrons doesn't weaken the diamond appreciably, but it does free up electrons to interact with visible light. Because boron absorbs lower-energy red light, the light that streams through has a blue hue.

The price of diamonds can vary greatly depending on size, cut, color, and other factors, including whether they have a history, but because of the rarity of blue boron diamonds, they often fetch more money than gems of similar quality. So remember this when you are in the jewellers with your partner to be.