We publish courtesy of Israeli Diamond Industry Blog
Author: Roe kalb
The word “diamond” comes from the Greek “adamas” – unbreakable or unconquerable. Diamonds are the hardest natural substance on earth, but they are not indestructible. When a diamond is placed in a microwave and the temperature is raised to 1405 degrees F (763 C), the diamond will vaporize, leaving nothing but carbon dioxide residue.
Diamonds are reputed to be 58 times harder than the second-hardest mineral on earth – corundum – which forms rubies and sapphires. Despite many attempts to use different tools to cut diamonds, eventually people figured out that only a diamond could cut another diamond. Nevertheless, despite their hardness, diamonds are brittle and will shatter if struck with a hammer.
Diamonds are formed over a very long time. Diamond formation takes place some 150 kilometers deep in the earth’s crust over the course of a billion years. Volcanic eruptions force them to the planet’s surface in a type of rock called kimberlite.
Other diamonds are found in or by rivers (alluvial deposits) or even in the sea floor, as in off the coast of Namibia. The largest known diamond in the world is the Cullinan, which was found in South Africa and originally weighed 3000 carats.
The original rough Cullinan was three times larger than the world’s next-largest diamond, the Excelsior, which was also unearthed in South Africa. Later, the Cullinan was cut into the 530.2-carat Great Star of Africa, the 317.4-carat Star of Africa, and several other diamonds, which are now part of the British crown jewels. The largest documented polished diamond is the Unnamed Brown, now known as the Golden Jubilee, which in its rough form weighed 700 carats and totaled 545 carats after being cut – a process that took three years.
The Centenary Diamond, another British crown jewel, also took three years to be cut. At a weight of 273.85 carats, it is reputed to be the largest flawless diamond.
Not all diamonds are white. Impurities or exposure to certain elements during formation can give diamonds a blue, gray, orange, red, pink, yellow, green, or black color, with vivid blue, pink, and green being the rarest. While diamonds themselves are plentiful, only some 20% are rated gem-quality (appropriate for jewelry). The rest are used primarily in industry.
Progress has been made in developing synthetic diamonds. Under the recipe devised by scientist James Ballantyne Hannay, lithium is mixed with paraffin and bone oil, and then heated in iron tubes. Modern methods involve crystallizing carbon under immense pressure. Because synthetic diamonds are cheaper than natural diamonds, but not even industry experts can tell them apart, they are becoming a big business.
Diamonds are weighed differently from gold. The gold karat measurement indicates purity, whereas a diamond carat refers to weight, with one carat equal to 200 milligrams. The term carat derives from the Arabic qirat (carob). In ancient times, gem traders would weigh stones against carob seeds because of the seed’s almost-perfect uniform size and weight. The same carat measurement applies to both natural and synthetic diamonds.
The custom of wearing a diamond engagement ring on one’s fourth finger comes from the ancient Egyptians, who believed that the “vein of love” ran directly between the fourth finger and the heart. And on the subject of diamond engagement rings, the tradition dates back to the Archduke Maximilian, who presented his fiancée, Mary of Burgundy, with a diamond betrothal ring.
The famous slogan “A Diamond is Forever” is often associated with diamonds. The ad campaign launched in 1947 to push diamonds to a wider consumer market. The strategy worked, and “A Diamond is Forever” was voted the best ad slogan of the 20th century.