The Essential 4C's
Anatomy Of A Diamond And The Effects Of Light
Marking
A diamond consists of two key sections, the Crown and the Pavilion. Their structure and relationship to each other in table form and depth percentages have the greatest impact on the diamond’s brilliance
The round brilliant cut was used as an example, because most other diamond shapes (“fancy cut” diamonds) have more complicated cut grading (which is why their cut grading doesn’t appear on certificates like GIA).
Diameter: The width of the diamond at the widest point of the girdle (for fancy cut diamonds, use the smallest diameter).
- Table Size: the largest facet at the top
- Crown Angle: The top part of the diamond between the waist and the table
- Girdle Thickness: The narrow band from the widest point of the diamond
- Pavilion Angle: The lower part of the diamond between the girdle and the buckle
- Culett: The fact from the bottom tip (preferable when not visible to the naked eye)
- Depth: The height of a diamond from the table to the cut
The science behind a diamond’s brilliance depends on its great ability to bend, slow and direct light as it passes through. The cut of a diamond determines how well the diamond is at redirecting light back through the surface of the diamond. Light travelling at about 187,000 miles per second when passing through a diamond is slowed to about 78,000 miles per second, close to the maximum for any other transparent substance (another reason we’re LV’57DIAMONDS).
All these elements contribute to the appearance of a diamond.
These qualities combine to give the life of the diamond and the way it reacts to light and the environment. The planning, the proportions, the precision of the cut and the details of the execution determine how brilliant, dispersive and sparkling the diamond will be. If the human-controlled cutting factors are not optimised, the appearance of the diamond can be adversely affected.
Diamond faceting has changed over time, especially with the evolution of lighting. There are many shapes and cuts, each with different visual characteristics. The most popular diamond in the age of modern electric lighting is the round brilliant.
Diamonds are known for their ability to transmit light and sparkle so intensely. We often think of a diamond’s cut as a shape (Round, Heart, Oval, Marquise, Pear), but which diamond cut is actually cut means how well a diamond’s facets interact with light. Shaping a stone so that its proportions, symmetry and cut allow the magnificent return of light that is only possible in a diamond requires precise artistry and workmanship.
Getting the best cut for a diamond is reflected in the final beauty and value of the stone. Of all the 4C’s, cut/grind is the most complex and technically the most difficult to analyse. To determine the cut grade of the standard round diamond – the shape that dominates the majority of diamond jewellery – GIA calculates the proportions of those facets that affect the appearance of the diamond from above. Using these proportions, GIA can assess what the best cut is for a diamond by examining how successfully a diamond interacts with light to create desirable visual effects.