According to the world leader in gemological research, the Gemological Institute of America (GIA), all polished diamonds are valuable. Although each diamond is unique, you know you will get a fair price because their value is judged objectively.
Since the 1940s, the GIA has provided a worldwide standard for determining diamond value and quality. Your diamonds are evaluated based on the 4Cs: color, cut, clarity and carat weight.
Color
Diamonds that are the most clear and lacking in color are the most valuable. Colors are graded on a scale from D to Z:
| Grade | Description |
|---|---|
| D to F | Colorless |
| G to J | Near colorless |
| K to M | Faint |
| N to R | Very light |
| S to Z | Light |
These differences are not visible to the naked eye. Diamonds are graded by comparing them to masterstones (brilliant diamonds of known color) under controlled conditions.
Cut (affected by the shape)
Each diamond shape is cut in a different manner to enhance the sparkle and brilliance. Diamonds come in ten common shapes plus more exotic shapes, including:
- Asscher
- Baguette
- Bullet
- Cushion
- Emerald
- Half moon
- Heart
- Horse head
- Marquise
- Old mine
- Oval
- Pear
- Princess
- Radiant
- Rose
- Round
- Royal Asscher
- Trillion
Cut is evaluated by the ideal depth for the stone. Shallow cut diamonds lose brilliance because they lose light from the bottom. Deep cut diamonds appear dull and less bright because they lose light from the sides.
Round diamonds are the most common, and GIA provides a five-point cut scale from poor to excellent to value a diamond’s cut. Appearance is valued based on:
- Brightness: total reflected light
- Fire: dispersion of light into the colors of the spectrum
- Scintillation: sparkle, flashes of light, and patterns of light and dark areas
The remaining four components of the round diamond’s assessment are weight ratio, symmetry, polish and durability.
Clarity
Diamonds are judged by the number of flaws they contain. Flawless diamonds are extremely rare, so most diamonds will have some flaws. Surface flaws are known as blemishes, while flaws within the stone are called inclusions. The degrees of flawlessness are defined as:
| Grade | Meaning |
|---|---|
| FL | Flawless, containing no flaws internal or external |
| IF | Internally flawless |
| VVS1, VVS2 | Internal inclusions difficult to see even with 10x magnification |
| VS1, VS2 | Internal inclusions visible at 10x magnification |
| SI1, SI2 | Inclusions visible at 10x magnification and possibly with the unaided eye |
| I1, I2, I3 | Visible inclusions that may affect brilliance and transparency |
Most diamonds grade as VS or SI. The fewer flaws, the more valuable the diamond.
Carat weight
Diamonds are weighed in very precise measurements to the hundredth decimal point. Each carat is 200 milligrams, or .2 grams, or .007 of an ounce.
A carat can be divided into 100 points to express fractions of a carat, so a half-carat diamond could also be referred to as a “50 pointer.”
While larger diamonds are more valuable than smaller diamonds of the same quality, the value of a diamond is based on all of the 4Cs, not simply the weight.
Selling a diamond?
Our buyers are trained in the GIA 4Cs and price diamonds against the Rapaport Price List, certified or not. Read our gemstone guide, see how we buy diamonds, or ask for a free evaluation.