A diamond is the hardest natural substance on earth, but if it is placed in an oven and the temperature is raised to about 763 degrees Celsius (1405 degrees Fahrenheit), it will simply vanish, without even ash remaining. Only a little carbon dioxide will have been released.
Diamonds are formed over a period of a billion or more years deep within earth’s crust – about 150km (90 miles) deep – and is pushed to the surface by volcanoes. Most diamonds are found in volcanic rock, called Kimberlite, or in the sea after having been carried away by rivers when they were pushed to the surface.
A diamond is 58 times harder than the next hardest mineral on earth, corundum, from which rubies and sapphires are formed. It was only during the 15th century that it was discovered that the only way to cut diamonds was with other diamonds. Yet, diamonds are brittle. If hit hard with a hammer, a diamond will shatter or splinter.
The largest diamond
The world’s largest diamond was the Cullinan, found in South Africa in 1905. It weighed 3,106.75 carats uncut. It was cut into the Great Star of Africa, weighing 530.2 carats, the Lesser Star of Africa, which weighs 317.40 carats, and 104 other diamonds of nearly flawless color and clarity. They now form part of the British crown jewels.
The Cullinan was three times the size of the next largest diamond, the Excelsior, which was also found in South Africa. The world’s largest documented polished diamond – unearthed in 1986, also in South Africa – is called Unnamed Brown. It weighs 545 carats and was cut down from a 700 carat rough diamond. It took an international team of expert cutters 3 years to complete the masterpiece. Another impressive diamond that also took 3 years to cut, and also is part of the British crown jewels, is the Centenary Diamond. It weighs 273.85 carats and is the world’s largest flawless diamond.
The biggest diamond in the entire universe is thought to be Lucy, a crystallized white dwarf star, a star consisting of diamonds. It’s weight is 10 billion trillion trillion carat. Named after the Beatles song, Lucy in the Sky with Diamonds, it is technically known as BPM 37093.
Not all diamonds are white. Impurities lend diamonds a shade of blue, red, orange, yellow, green and even black. Vivid blue, green and pink mined diamonds are the rarest. They are not the rarest gemstones, however. That title goes to a pure red ruby. Diamonds actually are found in abundance; thousands are mined every year. 80% of them are not suitable for jewelery – they are used in industry or in cheap rings.
Late in the 19th century, Scottish scientist James Ballantyne Hannay mixed lithium with bone oil and paraffin, sealed it in iron tubes and heated it to red hot. He claimed, in 1879, the resultant stones were diamonds. They were stored away and only many years later they were found to be diamonds, albeit synthetic. In 1892, Henri Moissan theorized that diamonds could be synthesized by crystallizing carbon under pressure. Today, synthetic diamonds is big business, outselling mined diamonds by far. Sometimes called cubic zirconia and synthetic moissanite, they are categorized and evaluated with the same grading scale process as mined diamonds but sell for much less. Synthetic moissanite is a diamond simulant with similar thermal characteristics to mined diamonds and most people, even so-called experts, can’t tell them apart.
A diamond carat differs from a gold carat. The gold carat indicates purity – pure gold being 24 carats. One diamond carat, for mined or synthetics diamonds, is 200 milligrams (0.007055 oz). The word carat derives from the carob bean. Gem dealers used to balance their scales with carob beans because these beans all have same weight