Most all natural diamonds contain small quantities of nitrogen atoms that displacing 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 in Fig. 1 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
Fig. 1
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 of the pavilion (Fig. 2), and not by looking at the top of the stone, as in our Fig. 3 example below. Color grading by 'visual-observation is performed against a Master CZ Colored Grading Set.
Fig. 2
Sarin Color Typing
is a relatively new sub-classification of the D through Z gading scale. Each classification is divided into five sub-classifications (D1, D2, D3, D4, and D5). Using a Sarin Diamond Colorimeter DC3000 (aka Gran Colorimeter), jewelers and gem labs can accurately provide a 'color typing' printout of a diamond's color grading that is compatible with AGS, GIA-GEM, IGI, and HRD grading scales. For the consumer, it is extremely benificial to know if your 'F' is a strong 'F,' or a borderline 'G.' Unfortunatly, most gem labs do not currently provide color-typing data in their reports and certificates.
Fig. 3
Golconda Diamonds
Type IIa diamonds (aka Golconda Diamonds) are colorless stones containing negligible amounts nitrogen or boron impurities to absorb the blue end of the color spectrum. These colorless stones, sometimes referred to as "white diamonds," "whiter than white," or "D+," are named after the famous Golconda Diamond Mines located in the state of Hyderabad, India.
D-Flawless - The Holy Grail
Large D-flawless diamonds (those weighing more than 2 carats) are some of the rarest minerals on earth. Only around 600 D-flawless roughs are cut into gems weighing between 1 and 2 carats during a given year, according to the GIA. Even with microscopic inclusions, fewer than 5,000 D-color diamonds weighing over half a carat are found each year.
Diamond Fluorescence
Approximatly 1/3 (35%) of all diamonds have a tendency to fluoresce when exposed to ultra-violet (UV) light. When diamonds are viewed under a UV light-source, they tend to fluoresce as blue. This fluorescent effect can be beneficial to a diamond that has a yellow tint, as the blue fluorescence will cancel out some of the yellow, making the diamond appear "colorless," but the diamond will have a dull, murky appearance when compared to a non-fluorescing diamond. Ultra-violet light is a component of natural sunlight and artificial 4800k to 5000k color-proofing light, so this effect will be more apparent under natural daylight than under artificial incandescent light. See Color in Gemstones for more information.
For diamonds with a color grading of D through H (colorless), fluorescence can negatively impact the value of the stone by 3% to 20%. On the other hand, diamonds with a poorer color grading (I through K), fluorescence could increase the value by 0% to 2% buy improving the color (or lack thereof). Fluorescence is graded as none, faint, medium, and strong.
Skin Tone and Settings
While some may prefer a very transparent D to F range, others may prefer a "warmer" color found in a G to J range to compliment their skin tone. In some settings with various combinations of other stones, diamonds with a visible tint may be preffered.
On To:
Fancy Colored Diamonds
Diamond Enhancements & Treatments
Colored Gemstone Grading Certificates & Reports
Diamond Chemistry & Composition
