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Union University Department of Physics

The Science Guys

Science Guys > August 2004

August 2004

What is the biggest diamond ever discovered and how are they made?

Gemstones are tokens of love but have caused bloodshed, they enchant but have toppled kingdoms. Gems are priced according to their rarity, durability, and beauty. Having all of those qualities, diamonds are therefore one of the world’s most sought-after commodities.

Diamond is a crystalline form of carbon, an abundant element. Diamonds only form under conditions of intense heat and pressure, perhaps 125 miles underground, and are brought to the surface by volcanoes. Most of the world's diamonds are mined in the remnants of ancient volcanoes, such as the volcano pipes of South Africa.

Not many diamonds have been found in America; however, the Crater of Diamonds State Park in Arkansas has yielded some that weighed a few carats. The most famous is the 4.25 carat, yellow Kahn Canary diamond. It was mounted as an uncut stone because it is so beautiful in the rough. If you go to the Crater of Diamonds, you can dig for your own gemstones and keep what you find!

In 1905, a mine superintendent for South Africa’s Premier Mines discovered a massive 3,106 carat gem-quality diamond. Hailed the Cullinan Diamond, it was as large as a man’s fist and yielded the 530.2 carat Star of Africa, the world’s largest cut diamond. The Star of Africa is now part of the British crown jewels.

However, God’s creation is more fascinating than we can imagine. Since diamonds need ultrahigh pressures to form, are there other places in the universe where one might find similar conditions?

Physicists at Berkeley produced diamonds by squeezing methane at humongous pressures in an anvil-like apparatus. The pressure obtained in these experiments was about 100,000 pounds per square inch. A laser beam simultaneously heated the system to about 2700 degrees F and tiny diamonds were formed. The researchers believe that in these kinds of severe conditions found in the interior of planets, diamonds might be the size of boulders!

Stranger still, the core of dead stars might be crystalline diamond! After stars, similar to our Sun, burn their hydrogen and helium, they collapse into white dwarf stars and shrink to the size of the Earth. Astrophysicists predicted when these white dwarf stars cool and shrink, most of the remaining material of the star, which is carbon, crystallizes.

Recently, astronomers showed experimentally that the white dwarf, BPM 37093, pulsated or "rang like a bell," a condition consistent with the theory that the star’s core becomes crystalline. Since pressures in white dwarf cores are millions of times anything produced on Earth, the crystal structure of the carbon is not exactly the same as diamond, but similar. Therefore, the researchers stated that the core of this white dwarf was "diamond-like." Imagine a diamond hundreds of miles in size!

Of course, on a white dwarf you’d weigh 300,000 times more than on Earth! We’re not going to mine this stuff, at least not anytime soon.