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How diamonds are cut and polished

Diamonds aren't pulled right from the earth in pear, heart, or round shapes, then shipped to jewellers and put in a ring. Even when they're in that early rough form, though, a diamond cutter typically has a plan in mind for that final gorgeous shape that might end up in your ring. Such vision reduces waste and contributes to precision along the way. Since diamonds are the toughest of minerals, how are they actually cut and polished to add to something like a beautiful ring or necklace?

Cutting the diamonds

One method of diamond cutting is called ‘cleaving‘. Much as the word implies, this kind of cutting splits, or divides, the diamond from an unwieldy shape into a smaller, workable one. To cleave a diamond, a strong mould (made of wax or cement) holds the diamond in place. A laser then makes a groove in the diamond that a steel blade fits into. Something strikes the blade in the groove, and the diamond breaks into two pieces. Cleaving only works if the diamond already presents a plane of weakness for the groove to go. If there’s no plane of weakness, sawing can work. For sawing, the cutter must use a blade that rotates about 15,000 revolutions per minute. A laser cut can also work if cleaving isn’t an option, but a laser cut will take hours longer than sawing.

The shaping process

Once a rough diamond is cut down to a more manageable size, a technique called ‘bruiting‘ gives it its shape. The only way to cut a diamond by hand is to employ other diamonds. This technique involves two stick-like instruments with cement at the tip to hold the diamonds in place. Using skill and dexterity, the diamond cutter holds these sticks and rubs the diamonds together where he wants them to shape. Bruiting can also happen mechanically, where two diamonds are placed on a spinning axle, so they can make one another round.

Creating a beautiful shine

A spinning wheel is typically used to polish the diamond once it’s in circular form. This ‘polishing‘ is what gives the diamond its facets. While polishing, it’s important to make the facets smooth so that each one holds as much reflective power as possible, as we’re drawn to diamonds for their luster  ̶  for the way they capture and make light move.

Additional considerations

While diamonds won’t melt in lava, and take almost 1,300 degrees Fahrenheit to melt in air, they’re known for their ‘fire‘. Fire, in relation to a diamond, is how much dispersed (flashes) of light appears. If a diamond is overwhelmed by sparkles, it will be harder to see its flashes of fire, and diamond cutters know this when they’re determining what kinds of cuts to make. Along with fire, cutters also take into consideration scintillation (the way light moves across the surface of the diamond) and brilliance (brightness and contrast). Diamonds can be cut into many shapes: round, oval, emerald, hearts. Overall shape and precise facets define how light and diamond interact, to produce a variety of options crafted from fine technique.

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