Diamond Information Girdle
The girdle runs around the edge of the diamond at its widest point. It is measured in terms of thickness. Most laboratories grade the girdle using words from extremely thin to extremely thick .It is also given as a percentage of the overall depth between 0 and 7%.
The Accredited Gem Appraisers (AGA) reccomend a girdle between 1.7% -3% , or in words , a girdle ranging from Thin to Medium , Medium to slightly Thick, for a perfect ideal cut. An extremely thin girdle is a much higher risk of chipping, whilst an extremely thick girdle can make the diamond awkward looking in a setting. The girdle can be faceted or polished. A faceted girdle gives a better look. When looking at the girdle you must stay away from large tolerances. For example, an extremely thin to extremely thick girdle will be visually wavy and detract the stones beauty.
Marcel Tolkowsky was a pioneer in the world of diamonds, and was the first person to present a mathematical analysis of diamond cut. In 1919 he released the 'Diamond Design' , A study of the reflection and refraction of light in a diamond. He concluded that a diamond , having the most perfect fire and brilliance should have a single set of proportions. A diamond with no culet and an extremely thin girdle should have a 53% table, crown angle 34.5° , crown height 16.2% , pavillion angle 40.75° , pavillion depth 43.1% and an overall total depth of 59.3% . One must remember though that Tolkowsky's set of proportions will be different for any diamond that has a culet or a thicker girdle
