Round Brilliant Cut
Rounds are the most popular shape that diamonds are cut into. It is also the most brilliant of all the cuts. You may have heard of a term called "Ideal Cut". This term refers to the attempt to cut a diamond into the best proportions to achieve maximum brilliance. The following is a breakdown of what is considered "Ideal Cut" in round brilliants according to "American Ideal / Tolkowsky" and the "European Ideal Cut" (Proportions are given relative to the girdle diameter):
"Ideal Cut" for Rounds
| |
American Ideal /
Tolkowsky |
European Ideal |
| Total Depth |
58.7 - 62.3% |
60.0 - 61.1% |
| Table Diameter |
53.0 - 58.0% |
57.5% |
| Girdle Thickness |
medium
to
slightly thick |
very thin
to
medium |
| Culet Size |
none
to
medium |
none
to
medium |
| Crown Angles |
34.3º to 34.7º |
34.5º |
| Pavilion Depth |
43.1% |
43.1% |
| Finish |
very good
to
excellent |
good
to
excellent |
| Crown Height |
16.2% |
16.2% |
Be aware that there is a premium for purchasing "Ideal Cuts", and they are more rare in the market. Cutting to "Ideal" generally entails losing more weight from the rough diamond than regular proportions.
There are 58 facets in a Round Brilliant Cut including the culet. On the Crown or upper part of the Diamond, these consist of 1 table facet, 8 bezel facets, 8 star facets, and 16 upper girdle facets for a total of 33. On the pavilion, or bottom part of the diamond, there are 16 lower girdle facets, 8 pavilion main facets and 1 culet.
Rounds are the most expensive cuts, and with good reason. It is usually possible to retain more weight from a Rough (unpolished) Diamond if it is cut into a Fancy shape than if it is cut to a Round.
Plot diagram for Round Brilliant Cuts:
This is the plot diagram that labs use to grade round diamonds:
Notable Round Engagement Rings:
Angie Harmon, Bvlgari Round Brilliant Cut with baguette side stones:
Pamela Anderson, 4 carat solitaire with yellow gold band:
Christina Aguilera, Round Brilliant Cut, bezel set in a cathedral semi mount:
Barbara Streisand's Ring:
Ali Landry's Engagement Ring:
 
Mary J Blige's Round Brilliant:
Carmen Electra's Engagement Ring
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DIAMONDS TUTORIAL NAVIGATOR
Preface:
Real Graders Don't Drink Kool-Aid
Lesson 1, The 5Cs:
Carat, Color, Clarity, Cut, Cost
Lesson 2, Shapes:
Round, Asscher, Cushion, Emerald, Heart,
Marquise, Oval, Pear, Princess, Radiant
Lesson 3, Articles:
How to Buy a Diamond, How to Sell Your Jewelry,
How to Read a Diamond Certificate,
The difference between a Certificate & an Appraisal,
What is the SI3?,
World's Largest Polished Diamonds,
World's Largest Rough Diamonds, Diamond Facts
Gem labs and the science, art and marketing of diamonds
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