Diamond Color Scale
The Gemological Institute of America's (GIA) Diamond Grading System grades diamond color on a letter scale of D (colorless) through Z (light yellow or brown):
D, E, F - Grades of colorless diamonds. D is the highest grade.
G, H, I, J - Grades of near-colorless diamonds.
K, L, M - Grades of faint yellow diamonds.
N, O, P, Q, R, S-Z - Grades of very light yellow diamonds.
Though diamond color is vitally important from a gemological point of view, it's highly doubtful that the untrained layperson could easily differentiate between a G color diamond and an I color diamond with the naked eye.
Diamond Clarity
Diamond clarity refers to each diamond's unique characteristics (flaws). Under the GIA International Diamond Grading System, clarity ratings are as follows:
Flawless Diamond (F) - No inclusions or blemishes visible under 10x magnification.
Internally Flawed Diamond (IF) - No inclusions and only minor blemishes visible under 10x magnification.
Very, Very Slightly Included Diamond (VVSI1, VVSI2) - Inclusions are difficult to see under 10x magnification.
Very Slightly Included Diamond (VS1, VS2) - Minor inclusions visible under 10x magnification.
Slightly Included Diamond (SI1, SI2) - Inclusions noticeable under 10x magnification.
Imperfect Diamond (I1, I2, I3) - Inclusions are obvious under 10x magnification and may affect brilliance and transparency of the diamond.
Clarity Enhanced Diamonds
Diamond clarity enhancement methods include use of a laser drill (to drill out inclusions in the diamond) or by means of fracture filling (filling tiny cracks with a clear, glass-like substance). Laser drilling does not affect the strength or durability of the diamond itself. Fracture filling results in repairs that can erode or darken over time. Additionally, a fracture-filled diamond generally does not have the durability or strength usually associated with diamonds.
Note Regarding Lab Created Gemstones
Lab created/synthetic gemstones have the same physical and chemical properties as natural gemstones, only they are created in a lab environment rather than by nature. The Federal Trade Commission defines lab-created and synthetic gemstones as possessing, "...essentially the same optical, physical, and chemical properties as the stone named."
The FTC requires that lab created and synthetic gemstones be identified as such and also requires that any enhancement treatment your gemstone has received must be fully disclosed by the seller, along with any special care requirements. For more information, please visit the FTC's Guides for the Jewelry, Precious Metals and Pewter Industries.