The Foundry Journal

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The Best Diamond Shapes: Round Brilliant Cut Diamond

Jan 04, 2016 BY Diamond Foundry IN Style Guide

A round brilliant cut diamond isn’t just one of the best diamond shapes – it’s the diamond shape. Created in 1919 by engineer and diamond cutter Marcel Tolkowsky, the round brilliant utilizes an ideal ratio to maximize its “fire” and brilliance. Unlike the old mine cut and other earlier ancestors, the round doesn’t focus on carat size. In fact, up to half the rough diamond is wasted in a round cut.

A round brilliant diamond in Zaven’s Taperd Pave ring.

Tolkowsky’s Proportions

A round brilliant cut diamond has 58 facets in an octahedron shape. Unlike other forms, the round isn’t cut too shallow or too deep, which prevents light from leaking out the bottom or the side. Instead, a round brilliant cut diamond shines out the top. While Tolkowsky wasn’t the first to suggest these new proportions, he gave the style its mathematical foundation. Diamond cutters had already begun to use techniques that emphasized light distribution at the cost of carat weight, thanks to large diamond deposits discovered in the ninetieth century.

Marcel Tolkowsky invented the ideal diamond cut.

Modern Popularity

The round is easily the most popular diamond shape.  It’s often used for engagement rings, though many earrings also feature round brilliant cut diamonds. Since it emphasizes brilliance over clarity, the round cut can help augment lesser stones with blemishes better than fancy cut alternatives. 


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