Diamond polishing is one of those little-known secrets—it makes a huge difference to the quality of the finished diamond, and yet most people don’t know too much about what goes into the last stages of preparing a loose diamond for sale.
According to a recent report in Science News, new research on diamond polishing may explain the way the surface of the diamond is prepared and given its characteristic sheen. A layer of liquid-like carbon on the diamond polishing wheel may make a huge difference in the look of the finished diamond. These innovations in loose diamond polishing may make a huge difference not only for loose diamonds used in jewelry, but could possibly allow scientists to hone loose diamonds in ways that would be useful in semiconductors or optics.
Of course, diamonds are polished using other diamonds, because they are the hardest minerals on earth. Diamond polishing, which has been essentially the same for 500 years, involves pressing the rough diamond against a cast-iron disk coated in a mixture of oil and diamond dust. The polisher needs to be careful to polish the stone along the natural crystal structure of the diamond; if he pushes against the grain, the loose diamond can be irreversibly scratched and will need to be cut again to a much smaller size.
The diamond polisher uses specialized equipment that combines an ancient method with modern technology.
Diamond experts always thought that polishing works by grinding off tiny bits of diamond and making the surface smooth. The recent study has discovered that what is really happening is that a tiny amount of liquid carbon is combining in the air with the oil and diamond grit to effectively polish the diamond.
But where does this liquid come from? Diamonds are made of carbon, of course, so when the loose diamond and the diamond grit make contact, a few carbon atoms in each form very strong bonds with each other, creating a mesh of loose atoms between the two surfaces. This liquid-like substance is highly reactive, says Michael Moseler of the Fraunhofer Institute for Mechanics of Materials in Science News, and the sharp edges of the diamond dust rip off individual chains of carbons and exposing them to the air.
This all sounds very cool and scientific, but remember that we are talking about what is going on at the molecular level—you can’t see any of this as its happening! Once the carbon is released from its bonds with other carbon atoms, it can bond with oxygen in the air, forming the common molecule carbon dioxide. It is this bonding of loose atoms into carbon dioxide that allows the surface of the diamond to become so smooth.
Each of these stones was individually polished to achieve that all-important smooth finish.
This helps explain why it is so important to polish a diamond in the right direction. The arrangement of carbon atoms is very precise; rubbed the wrong way, the tightly bound atoms will resist joining the inter-diamond layer, leaving irregular marks on the diamond itself.
Diamond polishers have always known that diamond polishing works, they just didn’t know the science behind it. This research may help improve the efficiency of the diamond polishing process, which could lead to better results and even better prices for everyone. But Jonathan Hird of the UCLA warns potential loose diamond buyers not to expect too much. “Diamond does not give up its secrets without a fight,” he says.
