Lucara Diamond Corporation

The World's Second Largest Diamond Has Been Unearthed in Botswana

Invaluable.

FIONA MACDONALD
19 NOV 2015
 

A Canadian mining company has unearthed the world's second biggest diamond in central Botswana. The 1,111-carat, gem-quality stone is the largest diamond discovery in over a century, and is dwarfed only by the Cullinan Diamond cut into the British Crown Hewels, which was an incredible 3,106 carats in its rough state.

 

Although it's safe to say the diamond isn't going to be cheap, no value has been placed on it as yet because it's too big to be assessed by an onsite scanner, so the Lucara Mining Corporation will now fly the jewel to Antwerp in Belgium to be valued. 

But the stone, which is the biggest to be found in Botswana, has already been classified a type IIa diamond – a category that makes up only 1 to 2 percent of all natural diamonds.

The classification means the diamond is almost or entirely devoid of boron or nitrogen impurities, which can creep into the carbon lattice, and it also suggests that it has incredible thermal conductivity. It's the second highest possible rating in terms of diamond clarity.

Add to that the fact that the stone also weighs 222 g and measures an incredible 6.5 cm by 5.6 cm by 4 cm, and it makes the as-yet-unnamed stone an incredibly rare find.

"The significance of the recovery of a gem-quality stone larger than 1,000 carats, the largest for more than a century … cannot be overstated," said Lucara Diamond chief executive William Lamb.

Lucara also confirmed that 24 hours after finding the 1,111 carat stone, it unearthed two other large diamonds, one sizing up at an estimated 813 carats. For a relatively small diamond company, it's a huge win, and Lucara's shares shot up as much as 37 percent on Thursday.

So how do diamonds this big form? Contrary to what you might have learned on the Internet, diamonds don't start out as coal. They're instead seeded from a range of carbon-containing minerals, which, under extreme temperatures and pressure, form diamonds over a time period ranging from 1 billion to 3.3 billion years.

What makes diamonds unique is the diamond lattice arrangement of its carbon atoms, which means that each carbon atom is strongly bonded to four other carbon atoms. This type of bonding gives diamonds their strength, and it all starts out with a group of carbon atoms in the same vicinity.

In the presence of a lot of pressure and heat, five carbon atoms will form special covalent bonds and create a crystal structure together. And over (very long periods of) time, more carbon atoms will add to this crystal structure, eventually growing into a diamond.

This all happens at depths of 140 to 190 km below Earth's surface, and the only reason we find diamonds today is that they moved up to the surface as a result of ancient, deep volcanic eruptions.

These eruptions don't occur anymore, which means that all the diamonds we're ever going to find are already in reach... and maybe the latest discovery and the Cullinan diamond are as big as they're going to get.

But it's fascinating to think that nature might still have some even larger clusters of carefully arranged carbon atoms stored down there somewhere, just waiting to be found.

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