Ideal Cut

The Ideal Brilliant Cut: Its Beginnings to Today


                “Ideal Round Brilliant Cut”

Since its beginnings in the early 20th century to the present day, confusion and misunderstanding has frequently surrounded the use (or misuse) of the term “Ideal Round Brilliant Cut,” its defining properties and origin. Some have advocated eliminating its use altogether. Through the examination of the Ideal Round Brilliant Cut’s evolution, this article endeavors to clear up its history, clarify its defining properties and in the process dispel the misunderstanding and mythology surrounding this most popular and important of diamond cuts.

Whether cut with the smaller table, larger pavilion main and shorter half facets of the early Ideal (Morse’s American Cut), or fashioned with the larger table, slimmer mains and longer halves of today’s Ideal, the images, Figures 20, 21, 24, 25 and 31 in this work ( Click here for full article (PDF) ) reveal the superior light performance of fire and brilliance that characterize the Ideal Brilliant Cut.

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.

Continue reading “The Central Ideal”

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







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