Guide to Diamond Cut
To many, cut is considered the most important of aspect of a gemstone’s quality and value. Diamond cut affects some of its optical and physical properties including how it reflects light and “sparkles.”
The Diamond Cut Process
Diamond cut refers to how the jeweler physically cuts the diamond stone into its shape and to the proportions and symmetry that achieve optimal light dispersion, which affects a diamond’s quality and price.
Each diamond is cut to very exacting standards. Let’s look at the process to cut a beautiful diamond to better understand the terminology the jewelry industry uses to explain diamond cut factors.
The most common cut, the round brilliant, has 58 facets, or small, flat, polished planes designed to yield the maximum amount of light reflected back to the viewer.
A diamond’s light reflection, known as brilliance, is an extremely important factor in evaluating the quality of a diamond’s cut. A poorly cut diamond will actually lose light and appear dull.
The widest circumference of a diamond is known as the girdle. Above the girdle of a brilliant cut diamond are 32 facets plus the table, which is the largest and topmost facet. Below the girdle are 24 facets plus the culet, or point.
Proportion diagrams will typically include the following information:
Depth: The height of a gemstone measured from the culet to the table.
Table: Located at the top of the diamond, the table is the largest facet of a diamond.
Girdle: Range of girdle thickness.
Culet: Appearance, or lack thereof, of the culet facet.
A diamond’s cut impacts four aspects of the stone’s optical and physical properties:
Luster: The quality and amount of light that is reflected off just the surface of the diamond. Luster is directly related to the hardness of the stone and the quality of its polish.
Brilliance: The amount of white light that is returned to the eye from both internal and external surfaces. Brilliance is determined by the quality of the diamond’s polish and the number and size of inclusions inside the gem.
Dispersion: The display of spectral or rainbow colors seen coming from the inside of a diamond. Often referred to as “fire,” dispersion is directly related to how well the stone is proportioned.
Scintillation: A diamond will show scintillation, or “sparkle,” when movement is involved. The viewer, the light source or the diamond itself must be in motion for scintillation to occur.
Guide to Diamond Carats
Carat weight is one of the 4Cs of diamonds that measures measures a diamond’s weight and size. The term "carat" is derived from the carob seeds that were used to balance scales in ancient times.
Today’s metric carat is equal to 200 milligrams, or one-fifth of a gram, and there are approximately 142 carats to an ounce. Carats are further divided into points. There are 100 points in a carat. A half-carat diamond may be referred to as a 50-point stone.
Because large diamonds are rare, they generally have a greater value per carat. When considering the value of a diamond or gemstone, two diamonds or gems of equal carat weight can have differing price points based on the quality of cut, color and clarity -- the three other diamond quality factors. A professional jeweler, like a member of Jewelers of America, is educated to distinguish and explain the various diamond quality factors so you find the highest quality diamond that fits your budget.
Guide to Diamond Color
Diamonds come in every color of the spectrum, but the most popular are colorless. Truly colorless, pure white diamonds are extremely rare and, therefore, the most costly. Laboratories, like the Gemological Institute of America (GIA), grade stones according to how far they deviate from the purest white as one of the diamond 4Cs.
The best way to see the true color of a diamond is by looking at it against a white surface. Colorless stones are graded D, E or F. All three grades are considered colorless but with slightly decreasing transparency. Color grading continues down through the alphabet, with each letter designating a slight darker or warmer tint.
Guide to Diamond Clarity
A diamond’s clarity, one of diamonds 4Cs, is affected by any external and internal characteristics created by nature when the diamond was formed or as a result of the cutting process.
Characteristics such as internal spots or lines are called inclusions. Although these marks make each stone unique, the fewer the inclusions, the more valuable the stone. Inclusions can sometimes interfere with the passage of light through the stone, diminishing the sparkle and value of the diamond.
According to the quality analysis system of the Gemological Institute of America (GIA), clarity is graded on a scale ranging from Flawless (Fl) to Imperfect (I). Only a tiny percentage of diamonds ever achieve a grade of Flawless.