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| Round Brilliant, Ideal,
and Old Mine Cut |
| A Round Brilliant Cut's measurements are expressed
as the depth and width. To measure the depth of the stone, measure
the length from the table to the culet (see Table and Depth
Percentage Formulas). The width or diameter is measured from
one side to the opposite side of the girdle. |
To determine the approximate weight of a Round Brilliant Cut
diamond, make the following calculation: |
Approximate carat weight of a Round Brilliant Cut diamond=Diameter
x Diameter x Depth x 0.0061 |
(The above weight formula provides an estimate. The actual weight
may vary up to 10%, depending on the make, girdle thickness,
and accuracy of the measurement tools.) |
The Ideal Cut diamond is the industry standard for a perfectly
proportioned Round Brilliant Cut diamond. It's has 58 facets,
and a Table % between 55% & 57%. Its Depth % is between 59.3%
& 60.9%. (See page 3 for formulas).
The crown encompasses 16.2% of the diamond's depth. The pavilion
is 43.1% of the diamond's depth. The crown is at a 34.5o degree
angle. The pavilion angle is 40.75o. |
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| An Old Mine Cut diamond was cut
over 75 years ago. It is characterized by a high crown, off round
shape, extremely large culet, small table, and very short lower girdle
facets. To recut an Old Mine Cut to a modern cut, the diamond will
lose 15-25% of its original weight. In order to estimate the value
of old mine cuts, grade the color and clarity of the diamond, deduct
15-25% from the original weight, and look up the price per carat on
the corresponding chart for the lower weight. |
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Round Brilliant
Cut MM and Corresponding Carat Weights
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Chart Not to Scale. Weights may vary up to 20% with make. Please
specify weight requirements when ordering.
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