Cut Grading
The quality of the cut is essential in diamonds' quality and value.
50% of the light is reflected from the surface of the crown and the remaining fifty is refracted into the diamond towards the pavilion, which is the most important part in a diamond. If the
pavilion is properly cut, light directed from the crown is entirely reflected back by the pavilion facets to the top.
Light reflected from the table is white whereas light that reaches the internal facets of the crown is refracted (like a prism) as mainly colored.
There are several terms used in diamonds grading that were generally established to determine the cut:
- Ideal
- This cut applies only to round diamonds.
- Calculated for getting the maximum of brilliance and fire.
- These are the ideal cut dimensions of a round diamond as calculated by Marcel Tolkowsky as part
of his Ph.D. thesis in Mathematics as mentioned on the AGS site:
- Round in shape, and brilliant-cut (58 facets)
- Depth percentage: 59%
- Table percentage: 53%
- Crown height percentage: 16%
- Pavilion depth percentage: 43%
- Girdle thickness: Medium and even all the way around the diamond
- Symmetry: Perfect
- Perfectly aligned and formed facets
- Very small or absent culet
- Premium
- Almost ideal (in many cases the cuts are the same for the two cases).
- Very Good
- Calculated to reflect most of the light that enters, but the proportions are slightly changed in order to create the effect of a larger diamond.
- Good
- Reflects much of the light that enters, the effect is calculated to be that of the largest possible diamond (optimum choice for an excellent cost-saving without sacrificing quality/beauty)
- Fair & Poor
- This cut reflects only a small quantity of the light that enters, the main goal is achieving the effect of great carat weight but with the cost of sacrificing other qualities. Avoid such cuts
This diamonds grading is to be found only on AGS certificates. On certificates issued by other similar institutions the diamonds' dimensions are specified instead — the width of the table, the width of the diamond, and the depth of the diamond.
Clarity Grading
The clarity grading of diamonds is performed under a 10x loupe magnification. As already mentioned in the previous lines, the clarity grades range from Flawless to Imperfect 3.
| Clarity | FL | IF | VVS1 | VVS2 | VS1 | VS2 | SI1 | SI2 | I1 | I2 | I3 |
| Scale | Flawless- Internally Flawless |
Very Very Slightly Imperfect | Very Slightly Imperfect | Slightly Imperfect | Imperfect | ||||||
- FL: Completely flawless
- IF: Internally flawless — only external flaws are present — can be removed by further polishing
- VVS1 — VVS2: slight inclusions hardly detectable even by expert under 10X magnification.
- VVS1 — inclusions detectable only viewing the bottom of the stone
- VVS2 — inclusions detectable from the top
- VS1 — VS2: inclusions detectable with a 10X loupe
- SI1 — SI2: the flaws are easily seen with a 10X loupe
- I1 — I3: flaws can be seen with the naked eye
- I2 — I3:It is highly advisable to avoid these diamonds.
Color Grading
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To achieve the highest degree of accuracy of color grading, stones must be loose, placed upside down for study, in best light and using proper equipment. Color cannot be graded for a mounted stone, as mounting color influences the color effect.
| GIA | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AGS | 0 | 0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | 5.5 | 6 | 6.5 | 7 | 7.5 | 8 | 8.5 | 9 | 9.5 | 10 | ||
| Colorless | Near Colorless | Faint Yellow | Very Light Yellow | Light Yellow | |||||||||||||||||||
- D-E-F
- Known as the colorless grades. D is reserved for larger diamonds whose colors can be more accurately graded. Diamonds of sizes under 0.5 carat usually get a top grade of F due to the greater difficulty in grading a small diamond.
- G-H-I
- Face white or face up colorless grades — appear colorless when viewed through the “face up” position or through the table. When turned upside down the stone will show a slight tint of color.
- J-K-L
- Diamonds of this range can appear colorless if cut well and can save the consumer a good deal of money.
- M-Z
- The yellow coloration increases continuously.
- Not advisable to purchase diamonds graded M-Z.
Fancy Colors
Natural colored diamonds are very rare and expensive. Diamonds have been found in almost every color of the rainbow.
Fancy colored diamonds are evaluated by the richness and beauty of the color. Of the existing diamonds grading systems, the most prevalent is a 9-layered scale developed by GIA, that ranges from Faint and Very Light grades(strictly speaking not fancy color grades) to Fancy Deep and Fancy Vivid (Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Deep, Fancy Dark, Fancy Vivid)
With colored diamonds it is hard to establish the origin of color whether natural or artificially induced — if not in laboratory conditions. When buying a fancy colored diamond make sure it has an origin-of-color report from a qualified gemological laboratory. The report will also indicate the color grade. Yet, the final choice is a matter of taste and does not lie necessarily within the parameters stipulated in a report.
Helpful suggestion: Always compare and examine more of the kind before purchasing one.
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