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### cut of diamond

The cut of a diamond determines how well it reflects light. This reflection is responsible for the gem’s brilliance or sparkle.
Skilled professionals cut the stone to mathematically exact proportions so as much light as possible reflects
from each of its mirror-like facets out the top of the diamond.
The diameter and depth of the gem affect how light travels within it and how light exits in the form of brilliance.
If the cut is too shallow, light escapes out the sides and the diamond loses brilliance.
If the cut is too deep, light is lost out the bottom and the diamond appears dark or dull.

 Diameter The width of the diamond through the girdle Table The largest facet at the top Crown The top part from the girdle to the table Girdle The narrow band around the widest part of a diamond Pavilion The bottom part from the girdle to the culet Culet The facet at the bottom tip. The preferred culet is not visible to the naked eye (graded "small" or "none") Depth The height from the culet to the table

 The two most important numbers to be looking for when looking for great cut are the depth percentage and the table percentage. -- Depth percentage is the depth of the diamond (table to culet) divided by the width of the diamond. The higher the number, the deeper the stone. The lower the number the shallower the stone. Table percentage is the length of the table divided by the width of the diamond. The higher the number, the bigger the table looks. The lower the number, the smaller the table looks. -- Out of Round: It is interesting to note that "round" diamonds are usually not perfect circles. The length and width measurements for a round are both diameter measurements and will be different for an out-of-round shape.

The following charts provide a summary of the top cut grades for round diamonds by the major grading laboratories.

AGS cut grade parameters
 American Gem Society (A.G.S.) Cut > Cut "0" Cut "1" Cut "2" Cut "3" Cut "4" Table width % 52.4 - 57.5 51.4 -59.5 51.4 - 61.5 50.4 - 63.5 50.4 - 65.5 Crown Height % 14.5 - 16.5 14.0 - 17.5 12.5 - 18.0 11.5-19.0 10.5 - 19.5 Crown Angle % 33.7 - 35.8 32.7 -36.3 32.2 - 36.8 31.7 - 37.3 31.2 - 37.8 Pavilion Depth % 42.2 - 43.8 42.2 - 44.3 41.7 - 44.8 41.7 - 44.8 41.2 - 45.3 Pavilion Angle 40.2 - 41.5 40.2 - 41.5 39.7 - 42.0 39.7 - 42.0 39.7 - 42.3 Girdle Thickness Thin to sl. Thick 0.51 - 2.95% Very thin to sl. Thick 0.091 - 2.95% Very thin to sl. Thick 0.091 - 2.95% Very thin to Thick 0.091 - 4.20% Very Thin to Thick 0.091 - 4.20% Total Depth% Not Addressed Not Addressed Not Addressed Not Addressed Not Addressed Culet size % Pointed to Med Pointed to sl. Large Pointed to sl. Large Pointed to Large Pointed to Large

PGS cut grade parameters
 Professional Gem Sciences (P.G.S.) Cut > Excellent Ideal cut Premium Cut Table width % 53 - 57 52 - 61 Crown Height % 14.0 - 16.5 13.0 - 17.0 Crown Angle % 33.5 - 35.5 32.5 - 36.5 Pavilion Depth % 42.5 - 44.0 42.0 - 44.5 Pavilion Angle 40.5 - 41.0 40.25 - 41.5 Girdle Thickness Thin to sl. Thick Very thin to Thick Total Depth% Not Addressed Not Addressed Culet size % Pointed to med: sl. abraded Pt to med: sl. abraded sl. nicked

EGL cut grade parameters
 European Gemological Labs, USA (E.G.L. USA) Cut > Ideal Cut Excellent Cut Very Good Cut Table width % 53 - 58 53 - 63 53 - 65 Crown Height % 13.0 - 17.0 11.5 - 17.3 9.5 - 17.8 Crown Angle % 33.0 - 36.0 32.0 - 36.3 31.0 - 36.8 Pavilion Depth % 42.0 - 44.0 41.5 - 44.5 41.0 - 45.5 Pavilion Angle 40.0 - 41.2 39.5 - 41.5 39.5 - 42.5 Girdle Thickness Thin to sl.Thick Thin to sl. Thick Thin to Thick Total Depth% 58.5-62.5 57.0-63.5 56.0-64.5 Culet size % Pt. to Med Pt. to Sl. Large Pt. to Sl. Large

GIA cut grade parameters

 Gemological Institute of America (G.I.A.) Cut > Cut "1" Cut "2" Cut "3" Table width % 53 - 60 61 - 64 65 - 70 Crown Height % 13.5 - 16.5 11.5 - 13.5 9.0 - 11.0 Crown Angle % 34.0 - 35.0 32.0 - 34.0 30.0-32.0 Pavilion Depth % 43 42.0 - 44.0 41.0 - 46.0 Pavilion Angle 40.5 40.0 - 41.5 39.5 - 42.5 Girdle Thickness Medium to sl.Thick Thin to Thick Thin to Very thick Total Depth% 59.0-61.0 58.0 - 62.0 Not Addressed Culet size % Not Addressed Not Addressed Not Addressed

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