An Australian diamond company has unearthed a 404.2-carat diamond, the largest ever discovered in Angola.

The Lucapa Diamond Company describes the nearly 3-inch-long stone, discovered in its Lulo mine, as not only huge but of spectacular quality. Testing has confirmed the diamond to be a Type IIa D-color gem or "virtually flawless." This designation alone puts it in a very exclusive club.

lulo gemThe Lulo gem is expected to fetch more than $14 million. (Photo: Lucapa Diamond Company)

"They contain either very little or no nitrogen atoms in the crystal structure," writes Canadian jeweler Reena Ahluwalia, adding that they represent only 1 percent to 2 percent of all the mined diamonds in the world. "Type IIa are so rare that they command a 5% to 15% premium, when they can be found."

The discovery of the Lulo gem comes on the heels of an apple-sized diamond unearthed in Botswana last November. The gem, the second-largest ever discovered, tipped the scales at a whopping 1,111 carats.

Recently named "Our Light," the Botswana stone will go on a road show under tight security before going up for sale later this year. For those interested in buying, good luck finding an estimate. As of right now, the gem is too big for conventional scanners to determine its full worth.

Lucara DiamondThe Lucara diamond, measuring 1,111 carats, may look like a chunk of ice, but don't be deceived. It's the second-largest high-quality diamond ever discovered on Earth. (Photo: Lucara)

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

'Virtually flawless' 404.2-carat diamond discovered in Angola
Massive 3-inch-long gem is estimated to be worth more than $14 million.