Diamond girdles tell a lot about diamonds and their cuts. To the average observer, girdles simply display the division between the top and the bottom sections of the diamond. As a matter of fact, the girdle plane is one of the most important features of a cut and polished diamond.


Girdles determine the contour shape of the diamond and its faceting placements which must compliment the diamond’s 3D structure in visual harmony.


Correct girdle positions are extremely crucial and allow craftsmen a base to navigate their cutting into acceptable and balanced faceted forms. If a girdle plane is in-line and evenly wide around the contour of the shape, it will allow for proportions to fall into place if facets are placed precisely and evenly (in conjunction with facet sizes, angles and azimuths.)


Evenly cut girdles will protect the diamond shape from unwanted accidents and allow for the efficient setting of the diamonds in their jewels.


In antiquity, natural girdles started appearing when cutters would cleave rough diamond crystals into point cuts or a bit later in time grind their tables down into table cuts (See figure 1).

Figure 1: Brilliant cut evolution

As time evolved and first faceting methods were discovered, faceting was utilized mostly to either cut out or disguise (hide) external irregularities and/or internal flaws (inclusions).


Cutters would apply randomly placed faceting which excluded any crown & pavilion divisions thus girdles were non-existing. Such cuts became to be identified as old Rose and Mughal Cuts etc (See figures 2a and 2b).

Figure 2a: Historic Diamonds

Figure 2b: The Kohinoor Diamond in its Mughal cut version

What are called knife edge girdles started appearing much later, when cutters understood that in order to reflect light from within a diamond it required a top portion (crown) which allows the light to enter and a bottom portion (pavilion) allowing the light to reflect back to the environment.


For a standard brilliant, cutters would start by cutting eight upper crown and lower pavilion facets in which their meet-point junctions formed natural knife-sharp edges and at the same time also determined the shape/contour of the diamond.


Knife edge girdles served as a dual purpose, one was the extremely thin border dividing the crown and pavilion while determining a shape and secondly, minimizing the girdle obstruction or reflections which usually reflected back from the pavilion facets when looking through the table of the diamond (fisheye diamonds). The thinner the girdles were (knife-edge) the less they were noticed and causing unpleasant visual obstructions.


Knife edge girdles means the sharp formation of the meeting points between crown and pavilion facets which excludes any girdle planes/facets (See figure 3).

Figure 3: A chip on a knife edge girdle (Photo courtesy of Michael Goldstein LTD.)

Free form and uneven wobbly girdles populated the Old Mine Cut era’s (17th – 19th century), such wobbly girdles would allow cutters to deliver a spreader diamond. Octahedrons don’t usually come with four naturally even girdles.


The picture below (Figure 4) attempts to show the real diameter if the diamond was cut to a balanced girdle.

Figure 4: A wobbly old mine cut diamond girdle (left) – approximate diameter “if” the girdle was balanced (right).

Girdles in modern times (20th century)

The way girdles were fashioned throughout the 20th century tell a lot about the evolution of diamond cutting. Girdle positions and thicknesses allowed cutters the freedom to control the final polished outcomes within a certain (but overly loose) standard, both in their lapidary works and final weight determination.

Cutters had plenty of room-play in order to game the value-system. This is a long and significant period prior to the development of early 21th century cut grades which today restricts such and other gamings of the system.

 

20th century girdle manipulations

  • Cutting diamonds with excessively thick girdles would save material loss resulting in heavier polished diamonds.
  • Uneven girdles would allow cutters to maximize surface areas (as shown in figure 4).
  • Brillianteering manipulations (digging & painting); digging would allow cutters to polish out natural rough skin and irregularities leftovers positioned usually by the girdle area which today force cutters to minimize diameters as solutions.
  • Painting allowed minimal weight loss for the brillianteering process resulting in a heavier final weight at a hefty play-of-light expense.
  • One excessive practice in the 20th century was the mass production of diamonds which would be cut to overly deep proportions with carat weights as priority, such diamonds would result in smaller surface to weight ratios and even worse, such proportions would not fully utilize the optical play-of-light abilities diamonds are known for.

Girdles into the future

Today cutters recognize the fact that if they don’t plan and position their girdles properly, they will have no chance to complete the cut to “excellent” satisfaction as widely expected. The girdle became the base of the cut, if not properly positioned on all aspects, the overall finished cut will never be absolute!

One exception still plays role, in fancy colored diamonds where color still rules, girdle objectives are different than in the colorless segment (D-Z). Overly thick girdles will help retain both rare material weight and optically play as reflected color retention areas.

The thicker the girdle plane surrounding the outline of the diamond the more color such areas concentrate. Pavilion girdle reflections are actually a standard cutting procedure in many fancy colored diamonds, they are cut to display color as a priority and the color concentrations in very thick girdles help reflect color instead of light.

 

A jeweler & setter’s nightmare!

Today, even though we offer old style appearances and character in our period cut diamonds, we still craft our diamonds with balanced girdles as to help the creation of jewelry become more efficient, more enjoyable for the craftsmen to work with.

Setting diamonds which possess thick and/or wobbly girdles will complicate the jeweler and setters crafts forcing manipulation of the setting and metal work. The jewelry creation becomes much more time consuming and the manipulation marks will always be visible.

When jewelers and setters receive well balanced cuts to work with, their creation process flows much better reflecting it in the finished jewels themselves. Jewelers appreciate the fact that we make sure our cuts & girdles are balanced all the time.

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