The Central Ideal

Have you heard of the ‘American Ideal’ or ‘Tolkowsky Ideal’ in diamond cutting? How about the ‘Morse Ideal’? Michael Cowing explains that because a majority of diamonds are fashioned as 57-facet round brilliants, many are familiar the ‘Ideal’ brilliant. Through their research GIA and AGS have both found ranges of angle combinations they believe retain the finest brilliance. However the two disagree over the extent of that range. Despite the controversy over these competing ranges, a surprising commonality—a Central Ideal—has been discovered, which we will explore here.

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Accordance in Round Brilliant Diamond Cutting

Photo realistic image of today's Ideal cut diamond

Photo realistic image of today’s Ideal cut diamond

Photo realistic image of the Ideal with pavilion cut in the antique style of the early 20th century

Photo realistic image of the Ideal with pavilion cut in the antique style of the early 20th century

Accordance in round brilliant diamond cutting

Michael Cowing, FGA

AGA Certified Gem Laboratory

 Abstract: Over more than 150 years, those involved in the diamond industry have worked to establish the ideal angles and proportions to cut the facets of the standard round brilliant (srb) cut diamond in order to produce the ‘Ideal’ gem. This paper reviews milestones in that work and demonstrates that the solutions by major contributors to this endeavour have surprising commonalities. These common aspects are in accord with the research and investigation of the author as well as that of the GIA and AGS and the knowledge of diamond cutters and the teaching of diamond cutting institutions.

Click to download the pdf: Accordance in Round Brilliant Diamond Cutting – published in Journal of Gemmology