Diamond Girdle

Girdle is the thin perimeter of a diamond, dividing the crown above from the pavilion below. When viewing a diamond in its setting or from a profile view, the girdle is the widest part (or the circumference) of the polished diamond - the portion of the stone that makes contact with the setting itself. When loose diamonds are measured, they are measured by the girdle to obtain length and width in millimeters.

A diamond girdle can be rough, polished or faceted. Brilliant cut diamonds (with triangular-shaped facets) usually have a faceted girdle rather than a perfectly round girdle; this gives the gem a higher measure of transparency. Step cut diamonds (with rows of elongated facets) usually have polished girdles that are not faceted.

what is a diamond girdle
 

Girdle Ratings

When a diamond is certified, it is measured at various points along the girdle to determine its thickest and thinnest points. If both points fall into the same category, a single rating is given. However, the girdle is most often rated as a range, such as 'Very Thin to Thick', to accommodate the variance between the thickest and thinnest points.

  • Extremely Thin: May be prone to chipping or breaking; care should be taken when setting stone
  • Very Thin: Very Good gemstone proportion; care should be taken when setting stone
  • Thin, Medium: Ideal gemstone proportion
  • Slightly Thick, Thick: Excellent to Ideal gemstone proportion
  • Very Thick: Good gemstone proportion
  • Extremely Thick: May make diamond look smaller, as more depth is taken up by girdle
Girdle Ratings | Brilliance.com

Buyer's Guide to a Diamond's Girdle

When purchasing a loose diamond, the girdle is not a significant consideration, as a thinner or thicker girdle will not necessarily have a significant impact on the appearance of an otherwise well-cut diamond. However, the variation between the thickest and thinnest points on the girdle is considered in the assessment of a diamond's symmetry, as a significant variation can make a diamond appear disproportioned. For those seeking ideal cut diamonds, we recommend looking for a stone with a girdle rated somewhere between Thin and Thick. A perfectly proportioned diamond would have a Medium girdle rating, though ratings close to Medium are also considered to be expertly cut.

The Effect of a Diamond's Girdle

A diamond with an extremely thin girdle has a slight risk of chipping along the girdle edge during setting or while being worn. For maximum protection, the diamond should be well-secured within the setting to minimize contact with hard or abrasive surfaces. A diamond with an extremely thick girdle will have great brilliance and fire, as long as it is cut to ideal proportions. However, an extremely thick girdle concentrates the diamond's weight in the middle, causing it to look smaller from the top than a diamond of a similar weight with a thinner girdle. When analyzing the impact of an extremely thick girdle on a diamond, it's important to evaluate the overall measurements of the stone. If the measurements are within the ideal range, the extremely thick girdle won't have a significant impact on the perceived size.

Diamonds with an extremely thick or thin girdle rating are sometimes priced lower than similar diamonds with ideal girdle ratings, offering a great value to the consumer. If you have selected a diamond with an extremely thick or extremely thin girdle, please contact a Brilliance Diamond Expert for a visual inspection before purchasing.

The Effect of a Diamond's Girdle

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