The cut of a diamond refers to its proportions. Of the 4C’s, the cut is the aspect most directly influenced by man. The other three are dictated by nature. Quite often the cut of a diamond is confused with its shape.
The cut of a diamond, its roundness, its depth and width, the uniformity of the facets, all determine a diamond’s brilliance. Many gemmologists consider cut the most important diamond characteristic because even if a diamond has perfect colour and clarity, a diamond with a poor cut will have dulled brilliance.
The width and depth have the greatest effect on how light travels within the diamond, and how it exits in the form of brilliance.
1. WELL CUT – When a diamond is cut to proper proportions, light is reflected from one facet to another and then dispersed through the top of the stone. Within the Well Cut standards are the Delphi Diamonds sub categories of Ideal, Excellent, Very Good and Good.
2. DEEP CUT – When the cut of a diamond is too deep, some light escapes through the opposite side of the pavilion.
3. SHALLOW CUT – When the cut of a diamond is too shallow, light escapes through the pavilion before it can be reflected.
Cut Determines Brilliance
The diamond’s proportion’s specifically the depth compared to the diameter, and the diameter of the table compared to the diameter of the diamond, determine how well light will reflect and refract within the diamond
Diameter: The width of the diamond as measured through the girdle.
Table: The largest facet of a gemstone.
Crown: The top portion of a diamond extending from the girdle to the table.
Girdle: The narrow band around the widest part of a diamond.
Pavilion: The bottom portion of a diamond, extending from the girdle to the culet.
Culet: The facet at the tip of a gemstone. The preferred culet is not visible with the unaided eye (graded “small” or “none”).
Depth: The height of a gemstone measured from the culet to the table.
Polish & Symmetry Affect Sparkle
Polish and symmetry are two important aspects of the cutting process. The polish grade describes the smoothness of the diamond’s facets, and the symmetry grade refers to alignment of the facets. With poor polish, the surface of a facet can be dulled, and may create blurred or dulled sparkle. With poor symmetry, light can be misdirected as it enters and exits the diamond. The polish and symmetry grades are clearly listed in each diamond detail page and within the GIA, DCLA, GSL diamond grading report. For the most beautiful diamond, look for a symmetry grade of ideal (ID), excellent (EX), very good(VG), or good (G) for an HRD graded diamond, and excellent (EX), very good (VG), or good (G) for a GIA graded diamond.
Avoid diamonds with symmetry grades of fair (F) or poor (P), as the alignment of their facets may misdirect light so severely that it affects the brilliance of the diamond. Diamond measurements are calculated and applied to a cut grading scale that makes it easy to understand how well each reflect light:
Ideal cut: Represents roughly the top 3% of diamond quality based on cut. Reflects nearly all light that enters the diamond. – An exquisite and rare cut. see Ideal Cut Proportions
Very good cut: Represents roughly the top 15% of diamond quality based on cut. Reflects nearly as much light as the ideal cut, but for a lower price.
Good cut: Represents roughly the top 25% of diamond quality based on cut. Reflects most light that enters. Much less expensive than a very good cut.
Fair cut: Represents roughly the top 35% of diamond quality based on cut. Still a quality diamond, but a fair cut will not be as brilliant as a very good cut.
Poor cut: This includes all diamonds that do not meet the proportion standards of a fair cut. These diamonds are deep narrow or shallow and wide and tend to lose most of the light out the sides and bottom. Delphi Diamonds does not carry diamonds with cut grades of poor.
Delphi Diamonds Cut – Delphi Diamonds carries a large selection of ideal and very good cut diamonds. You’ll find no diamonds with cut grades lower than good, which are too shallow or deep to present an acceptable amount of brilliance.
Which Cut Grade Is Best
For a diamond with the best cut, that will look exceptional even when viewed under a microscope, look to the Delphi Diamonds ideal cut collection. These diamonds reflect the most brilliance because they are cut to the most exacting proportions, and have the highest polish and symmetry grades for round diamonds, and have either excellent or very good for princess-cut, emerald-cut, and Asscher-cut diamonds.
For the best value in a brilliant diamond, choose a diamond with a cut grade of good or very good, and polish and symmetry grades of very good or good.
In an ideal – or very-good cut diamond with very good or good polish and symmetry, consider less expensive grades of colour and clarity — look for a diamond with G or H colour and SI1 or SI2 clarity.