Incredibly, most of what makes a diamond valuable occurs in the earth long before we ever see it. Controlling a diamond's cut is the one thing we can add to make a diamond even more brilliant.
Here are the primary things to consider about a diamond's cut:
• Proportion
• Symmetry
• Cut Grades
At the end of this section we'll summarize What to Look For in a Diamond Cut.
An expert diamond cutter can take a rough diamond and make it into a thing of beauty. Although each diamond is individual, the right cut should force light to refract inside the diamond at the right angle so that it bounces back straight out at your eye.
Why does a diamond sparkle?
Diamonds capture light and, ideally, bounce it straight back out. If a diamond is cut too deep or too shallow some of the light will be lost and reduce the brilliance of the diamond.
Proportion
Exact mathematics must be used to cut facets at just the right angles so that they match up with each other and refract light back out the top, or crown of the diamond. The crown must be proportional to the diamond and must alight perfectly to the bottom, or pavilion.
Each diamond is unique and the measurements are different for every cut, as well as for every diamond shape (marquise, brilliant, emerald, etc…). Experts separate the cuts for each diamond into three basic categories: Ideal, Premium and Good.
An Ideal cut brings out the most sparkle, the most brilliance in a diamond.
A Premium or Good cut will still have plenty of fire but will be slightly less valuable.
Newport Diamonds does not carry diamonds below Good quality (such as Fair or Poor cut diamonds), and each diamond is rigorously examined by a team of expert gemologists.
We use the classic Round Brilliant cut as our standard, below are our guidelines for determining an Ideal, Premium or Good cut.
The Gemological Institute of America will only grade the cut on Round Brilliant but diamonds. For other shapes, they will give the depth and table percentages and rate the stone's finish, which includes symmetry and polish.
Table percentage measures the width of the diamond table relative to the width of the stone at its widest point. The correct relationship will result in the best sparkle. If the relationship is off the diamond may not refract light properly and may make the stone appear duller and smaller than it really is.
Symmetry
If your gemological report includes symmetry, look for an Excellent, Very Good or Good rating. This means the facets align properly and that the crown is properly situated in proportion to the facets.
Round Brilliant Diamond Cut Grades
| Grade |
Table Percentage |
Depth Percentage |
| Ideal |
53% - 57% |
59% - 62% |
| Premium |
58% - 63% |
58% or 63% |
| Good |
64% - 65% |
57.5% or 64% |
What to Look For in a Diamond Cut
Look for a diamond with the right cut and symmetry in a shape you love. This will affect the diamond's fire and sparkle more than its' size, and along with the other 4Cs will give you the best diamond for your budget.
Note: When you receive your grading report, it may also mention fluorescence. A few diamonds fluoresce (glow) when put under ultraviolet light, which does not usually affect a diamond's value.
Go to Next Page: The 4 Cs: Color
