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21 Months to cut a Diamond?

21 Months to cut a Diamond?

On May 17th 2013, a stunning 101.73ct pear shaped diamond was auctioned by Christie’s at the Four Seasons Hotel des Bergues in Geneva and was purchased for a whopping $26.7M!

The stone was cut from a rough diamond found in the Jwaneng mine in Botswana. It originally weighed 236 carats and took 21 months to polish - but why does the cut and polish process take so long?

236 Carat Rough Diamond

Every element of the cutting process is focussed on producing a cut diamond that maximises both the size and the fire and brilliance of the diamond. “Fire and Brilliance” is essentially the stones sparkle. The Biggest Sparkliest Diamonds are the most desirable and therefore valuable!

The first, and most time consuming step is to very carefully examine the rough stone. Identifying the crystallization axis and mapping imperfections and inclusions will enable the Master Craftsman to determine the best shape for the cut diamond and create a “cutting map”, or plan for the cutting process.

Even with extremely careful planning, over 50% of the Rough Diamond’s carat weight is lost during the cutting process. The second stage is to split the rough diamond to form two separate stones each with a perfectly flat surface. The flat surface will become the table of the polished diamond. Traditionally the diamond is split along the chosen line by hammering a very thin steel blade with a short sharp hit. Nowadays diamonds are more often sawn than split. The saw that is used consists of a metal disc of which the edge is covered with diamond powder and oil.101 Carat Flawless Pear diamond

After the initial cutting the diamond is shaped in the numerous stages of polishing. Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming. Ideally 58 facets are shaped into the stone. These facets are made on a flat horizontal disc, covered with a mixture of diamond powder and oil. The stone, held by pincers, is forced against the surface of the disc just long enough to form the facet, and must be executed with extreme regularity at predetermined angles to maximise the stones fire and brilliance.

So, How does it take 21 months to cut a diamond? Sparkling perfection takes time to plan and skill to create. Rushing the process could lead to excessive diamond wastage, unnecessary ugly inclusions and poor shaping. The Diamond cutting business is a prime example of an industry in which “Slow and Steady” wins the day.


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