Diamond color is graded from D-F (colorless) through G-J (near colorless), K-M (faint yellow), N-R (very light yellow) down to S-Z (light yellow). In the K-R range you sometimes get a very light brown called "champagne" and a darker brown called "cognac", both very attractive. Even when a stone has a visible tint, such as an M color, it can still be very lovely if it has good clarity and cut.
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Diamonds also come in a wide variety of other colors, including red, blue, green and a bright yellow known as "canary." These are graded as Z+ and are known as fancy diamonds. Ones with good color are very rare and can sell for much more per carat than white diamonds.

It is very common for diamonds to be formed in nature with slight imperfections. These are known as inclusions and can come in many forms, including tiny white points, dark dots of carbon, or feathery cracks. The fewer inclusions, the more the stone is worth. A diamond's clarity ranking is determined by the number, size, type and placement of the inclusions.

The grading ranges from FL (flawless) through VVS (very, very slight imperfection), VS (very slight imperfection), SI (slight imperfection), I1 (imperfect, can be seen with the naked eye) to I3, commercial or industrial grade.

If cut properly a diamond reflects the light back up through the center of the stone to give its characteristic sparkle. A poorly cut stone looks flat like a piece of glass. The quality of the cut is call the "make", and it ranges from Class 1-Ideal Cut (round diamonds only), Class 2-Well Cut, Class 3-Average Cut to Class 4-Below Average Cut. There are six key factors that determine a diamond's class, but they need to be understood because diamond reports usually give the factors but do not classify them.

Most diamonds 1/2 ct and above come with a diamond report from a gem lab. Often they are fancied up and called "certificates" for marketing purposes, but--no matter how important they look--they are just educated opinions from trained gemologists.

About Diamond Clarity

A diamond's clarity grade is actually a flaw-grade and refers to the tiny imperfections present when the stone was originally formed by nature. If no flaws can be seen under 10X magnification, such as with a diamond loupe, it is considered "flawless".

There are 13 classes of flaws internal (inclusions) and external (blemishes), but the most common are dark spots of foreign material, tiny internal cracks called "feathers", and external nicks or chips.

The diamond clarity grades are as follows:
FL: Flawless. Cannot be seen with a 10X diamond loupe.
IF: Internally Flawless. Has tiny nicks or scratches that can be polished out.
VVS1, VVS2: Very, Very Slightly Included. Very, very difficult for a qualified observer to see under 10X magnification.
VS1, VS2: Very Slightly Included. Very small inclusions, very difficult to see by a qualified observer.
SI1, SI2: Slightly Included. Can be seen fairly easily by a qualified observer with a 10X loupe, and in some cases without magnification.
I1, I2, I3: Imperfect. Inclusions can be seen with the naked eye, but can be desirable stones at a much lower cost if they are brilliant and lively. Because I3 is the lowest grade used, be on the lookout for industrial grade diamonds not suitable for jewelry that have been classified I3.

FL and IF diamonds are extremely scarce and expensive, so are rarely used in jewelry. VVS stones are rare and priced at a premium, but VS diamonds are more readily available in good color and cut. With SI and I1 stones you find your bargains in good looking diamonds, and I2 should be the bargain hunter's choice for earrings that cannot be viewed up close.

Clarity grades dramatically affect the value of a diamond, but down to I1 have little effect on its beauty.

Clarity enhancement techniques are being used today and should be disclosed by reputable jewelers. The most common are lasering to remove black inclusions, fracture filling to hide cracks and heat or radiation treatment to lighted or change the color.