Most all natural diamonds contain small quantities of nitrogen atoms that displace the carbon atoms within the crystal's lattice structure. These nitrogen impurities are evenly dispersed throughout the stone, absorbing some of the blue spectrum, thereby making the diamond appear yellow. The higher the amount of nitrogen atoms, the yellower the stone will appear.

In determining the color rating of a diamond, the Gemological Institute of America uses a scale of "D" to "Z" in which "D" is totally colorless and "Z" is yellow. The color chart below explains the GIA grading system for clear (not fancy-colored) stones.

Diamond Color Designations

* D, E, F - colorless (white)
* G, H, I, J - near colorless
* K, L, M - faint yellow or brown
* N, O, P, Q, R - very light yellow or brown
* S, T, U, V, W, X, Y, Z - light yellow or brown

Due to a diamond's high brilliance, and dispersion of light (fire) when looking through the table or crown, color grading should be determined by examining the stone through the side, and not by looking at the top of the stone,

CUT

Diamond Cut Quality

When jewelers judge the quality of a diamond cut, or "make", they often rate "Cut" as the most important of the "4 Cs." The way a diamond is cut is primarily dependent upon the original shape of the rough stone, location of the inclusions and flaws to be eliminated, the preservation of the weight, and the popularity of certain shapes. Don't confuse a diamond's "cut" with it's "shape". Shape refers only to the outward appearance of the diamond (Fig. 5 below), and not how it is faceted.

The Importance of Cut Quality

When a diamond has a high quality cut (ideal cut), light will enter the stone through the table and crown, traveling toward the pavilion where it reflects from one side to the other before bouncing back out of the diamond's table toward the observer's eye. This phenomenon is referred to as "light return" (see below) which affects a diamond's brightness, brilliance, and dispersion. Any light-leakage caused by poor symmetry and/or cut proportions (off-make) will adversely affect the quality of light return.

The "Shallow Cut" and "Deep Cut" examples below show how light that enters through the table of a Modern Round Brilliant diamond reaches the pavilion facets and then leaks out from the sides or bottom of the diamond rather than reflecting back to the eye through the table. Less light reflected back to the eye means less "Brilliance". In the "Ideal Cut" example, most of the light entering through the table is reflected back towards the observer from the pavilion facets.

Four Cs Diamond Cut Quality

Keep in mind that the variance in proportions between an "Ideal Cut" (ideal make) and a "Fair, Poor, Shallow or Deep Cut" may be difficult to discern to the novice observer, although there will be a lack of brilliance, scintillation, and fire. Cut quality is divided into several grades listed below.

CARAT

Balancing Cut and Weight

A diamond or gemstone's "Carat" designation is a measurement of both the size and weight of the stone. One "Carat" is a unit of mass that is equal to 0.2 grams (200 milligrams or 3.086 grains) or 0.007 ounce. A carat can also be divided into "points" with one carat being equal to 100 points, and with each point being 2 milligrams in weight. Therefore, a 1/2 carat diamond would be 50 points, a 3/4 carat diamond is 75 points, and a 2 carat diamond is 200 points.

When a single piece of jewelry has multiple stones, the total mass of all diamonds or gemstones is referred to as "Total Carat Weight" or "T.W."

The word "Carat" is derived from the Greek word keration, or "seed of the carob". In ancient times, carob seeds were used to counterbalance scales, and as a benchmark weight due to their predictably uniform weight.

Diamond Carat Weight

Note: Your screen resolution may alter the reproduction size of the chart above. This carat/millimeter sizing chart is meant for comparison purposes only.

Occasionally, a stone cutter will need to make compromises by accepting imperfect proportions and/or symmetry in order to avoid noticeable inclusions or to preserve the carat rating of the rough stone.

CLARITY

All of the grades of diamond clarity shown in the table below, reflect the appearance of inclusions within the stone when viewed from above at 10x magnification. Higher magnifications and viewing from other angles are also used during the grading process. In "colorless" diamonds, darker inclusions will tend to create the most significant drop in clarity grade. In fancy-colored diamonds, light or pale inclusions may show greater relief, making them more apparent, causing a greater drop in grade.

Diamond Clarity Designations

* FL - "Flawless" no inclusions at 10 x magnification
* IF - "Internally Flawless" no inclusions at 10 x magnification - small blemishes
* VVS-1 - "Very Very Small" inclusions hard to see at 10 x magnification
* VVS-2 - "Very Very Small" inclusions. VVS1 better than VVS2
* VS-1 - "Very Small" inclusions visible at 10 x magnification - not naked eye
* VS-2 - "Very Small" inclusions VS1 is better grade than VS2
* SI-1 - "Small" or "Slight" Inclusions or "Imperfections" may be "eye clean"
* SI-2 - "Small" or "Slight" Inclusions or "Imperfections" visible to naked eye
* SI-3 - Inclusions large and obvious, little or no brilliance
* I1 to I3 - Imperfect, with large Inclusions, fractures, and flaws

GIA Grading System

The chart below explains the GIA grading system for inclusions and imperfections. Considerations in grading the clarity of a diamond include the type of stone, point size and the location of inclusions. Inclusions that are near to, or break the surface, may weaken the diamond structurally, therefore reducing its value significantly. On the other hand, it may be possible to hide certain inclusions behind the setting of the diamond (depending on where the inclusion is located), thus minimizing any negative impact of the inclusion.

Internal Diamond Inclusions

* Carbon - Tiny black spots caused by carbon inclusions (natts).
* Clouds - Grouping of tiny pinpoints that may not resolve at 10X Magnification, appearing cloudy.
* Feathers - Cleavage planes or internal fractures that have the appearance of feathers.
* Grain Center - Concentrated area of crystal growth that appear light or dark.
* Internal Graining - Irregular crystal growth resulting in internal distortions, waviness, or a haze.
* Needles - Rutile-like needle shaped inclusions.
* Pinpoints - Minute crystals within the diamond that appear white.
* Twinning Wisps - Inclusions resulting from crystal twining during growth.

External Diamond Inclusions

* Bearded Girdles - Fine cracks, chips, fringing, or feathers along the outer edge of the girdle.
* Bruising - A percussion mark caused by impact.
* Cavities - An indentation resulting from a feather or damage during polishing.
* Chips - Damage usually occurring on the sharp edge of a facet.
* Knots - An inclusion that penetrates the surface, appearing as a raised area.
* Indented Naturals - A natural indentation that was not removed by polishing.
* Filled Fractures - Fractures that have been artificially filled.
* Pits - Dislodged pinpoint inclusions at the surface.
* Surface Grain Lines - Visible surface lines caused by irregular crystallization during formation.

Fracture Filling

Diamond clarity is sometimes enhanced by filling fractures, much like repairing a crack in your car's windshield. Such diamonds are sometimes called "fracture filled diamonds". According to FTC guidelines, vendors should disclose this enhancement, and reputable filling companies will use filling agents which show an orange or pink flash of color. Ken K. Thompson Jewelry does not offer fracture filled diamonds.

There is a significant price discount for fracture-filled diamonds. The GIA will not grade fracture-filled diamonds, in part because the treatment isn't permanent. Reputable companies often provide for repeat treatments if heat causes damage to the filling. The heat generated by a blowtorch used to work on settings can cause damage, therefore it is essential to inform anyone working on a setting if the diamond is fracture-filled, so they can use greater care while working on the piece.

Laser Drilling

Laser drilling involves using a laser to burn a tunnel or hole to a carbon inclusion, followed by acid washing to remove the coloring agent. The drilling process leave tiny telltale shafts or tunnels that are visible under magnification.

The treatment is considered permanent and both the GIA and AGS will issue grades for laser drilled diamonds. The final clarity grade will be the grade that is assigned after treatment. Ken K. Thompson Jewelry does not offer laser drilled diamonds.

Human Caused Surface Blemishes

* Abrasions - Whitish haziness along the junction of facets caused by wear.
* Nicks - Small chips at facet junctions.
* Scratches - Grinding Wheel Marks of scratches from contact with other diamonds.
* Burn Marks - Surface burning from heat buildup during polishing.

"SI-3" is a grade sometimes used in the diamond industry. The designation of SI-3 was popularized by the EGL (European Gemological Laboratory) grading office.