Diamonds are a lab's best friend
We know they make the rich look richer, but most diamonds are used in industry, and synthetic diamonds are hot on their heels, writes JOHN HOLDEN
THEY USED TO be a girl’s best friend, but now they’re in demand as much from engineers in labs and factories as from glamorous celebrities: so what makes diamonds so special?
No one could ever accuse the diamond of being humble. Its association with glamour, wealth and extravagance was copper-fastened by the likes of Liberace, Elizabeth Taylor and J-Lo. But while diamonds may be better known as the trinkets of the rich and famous, only 20 per cent of those found or manufactured become jewellery. The other 80 per cent are used in industry.
Engineers in factories and labs surround themselves with the precious stone, and they make better use of them than celebrities. Diamonds have become essential in a variety of high-tech manufacturing processes. Their superlative physical properties mean they are used in industrial applications such as cutting, drilling, grinding and polishing.
“On the Mohs Scale of Mineral Hardness [measurement for scratch resistance of minerals], talc is at number one, as the softest, and diamonds are at number 10,” says Prof Martin Feely of NUI Galway. Feely runs the only course in gemmology in the country.
“Diamonds are made of carbon, and carbon is extraordinary in how it assembles at an atomic level. It gives you one of the softest metals – graphite – as well as diamonds at its hardest level.”
The chemical composition of diamonds and graphite is the same, and yet the two are very different. “This has to do with their atomic scaffolding: how atoms of carbon are bound together, and the architecture of that atomic structure,” says Feely. “If you take graphite, for example, you can rub it and carbon will come off on your thumb. That’s because the carbon atoms are bound together. They are actually in layers. At an atomic level they are held together by the weakest bonds in nature.
“In a diamond, each carbon atom is bonded to four other carbon atoms. These are very robust strong bonds. They have the same strength as graphite but each carbon is bonded to another atom rather than just being in layers.”
Natural diamonds are formed about 160km below the surface of the earth at temperatures of around 1,100 degrees at pressures in excess of 20 kilobars. “Imagine 160km of rock on top of you,” says Feely. “The pressure is immense. A diamond is formed there by the coming together of carbon atoms and there they reside in a diamond stability zone. At some point an eruption will occur with a fracturing of the rock above. The type of rock that brings the diamonds up is known as kimberlite [it was first discovered in Kimberly, South Africa].