Anatomy of a Diamond
Article By Admin
Feb 11, 2019
A diamond’s cut determines its fire, brilliance and scintillation, and hence, has an impact on its value. It directly relates to the craftsman’s ability to shape a diamond to the perfect proportion.
Through learning about the perfect proportion, you will learn to describe the anatomy of the diamond; or where the proportion measures. It should be noted that the quality of a diamond’s cut is not determine by a single proportion measurement, but a combination of many such measurements. There are certain terminology that are universal to describe specific part, or anatomy of the diamond.
There are six structures of a diamond on which the proportion measurement are based on. They are the table, crown, girdle, depth, pavilion and cutlet.
The table is the top horizontal facet of the diamond. The table size is the diameter measurement of this facet of the diamond. The average table size is usually expressed as a ratio to the average girdle diameter. In consideration with other proportion, an average table size between 52% and 62% would warrant an ‘excellent’ grade.
The total depth is the measurement from the top surface of the table to the bottom of the cutlet. It is usually expressed as a percentage of the average girdle diameter.
The pavilion is the lower portion of the diamond, from the bottom edge of the girdle to the cutlet. The pavilion depth is the measure of this proportion expressed as a percentage of the average girdle diameter. A well-proportioned pavilion will allow light to be reflected back to the crown of the diamond, increasing its brilliance. On the other hand, a pavilion that is too shallow, or too deep would result in light dispersing from the bottom and side of the stone.
Another important measure of the pavilion is the pavilion angle, which is the angle formed between the girdle plane and the pavilion’s main facet. With other proportions in their ideal range, a pavilion angle of 40.6° and 41.8° would be graded as ‘excellent’.
The crown is the upper portion of the diamond, from the top edge of the girdle to the top of the table. Its average height is usually expressed as a percentage of the average girdle diameter. An optimal crown proportion would maximise dispersion and hence the brightness of a diamond.
The other measurement of the crown is the crown angle, which is the angle formed between the bezel facet to the girdle plane. The bezel is the multi-faceted surface circumscribing the table of the diamond. A crown angle of 31.5° to 36.5° would result in a diamond being graded as ‘excellent’ when all other parameters are within the ideal range.
In addition, the star length measures the horizontal distance from the edge of the table to the point of the star facet. It is expressed as a percentage to the length of the table edge to the girdle edge. An ‘excellent’ graded cut would have a star length of 40% to 70%, with all other parameters being in the ideal range.
The girdle is the middle portion of the diamond. It is a narrow strip between the crown and the pavilion. A girdle thickness is described as a range, from its thinnest to its thickest side. An ideal girdle thickness would have a narrow range band, while not being too thin or too thick. Too thick a girdle would add unnecessary weight to the stone, resulting in a smaller appearance for a given carat size. On the other hand, too thin a girdle would result in the diamond being more fragile due to its shape corners. An ideal girdle would be described as ‘medium to slightly thick’.
The lower girdle / half facet length is a ratio of the length of the girdle facet to the length of the pavilion. The girdle facet is the facet extending from the girdle, pointing inwards. In contrast, the pavilion facet is the facet extending from the bottom of the pavilion, pointing outwards. This would affect the brilliance of a diamond. An ideal ratio would fall between 65% and 90%.
The cutlet is the small facet at the bottom of the diamond. It is there to prevent chipping and abrasion to the point. It is described as ‘none’, ‘very small’, up to ‘extremely large’. It is ideal that the cutlet is not visible to the unaided human eye, and when described as ‘none’, ‘very small’ or ‘small’ would correlate to the ‘excellent’ grade.
While every diamond is unique, all diamonds share certain structural features. A diamond’s anatomy, or its basic structure, determines its proportions, brilliance, dispersion and scintillation. Each part of the diamond has a specific name, and having a basic understanding of how each part contributes to the diamond as a whole will help you find your perfect diamond.