Diamond Tutorial

Cut

In the late 17th century, an Italian jeweler invented the "brilliant cut," a round-shaped cut that remains the optimum - and most popular - choice for maximizing a diamond's brilliance and beauty.� The modern round brilliant cut has 58 facets - 33 on the top, 24 on the bottom, plus the bottom point, called the culet.� Two of�the most important factors are a stone's depth percentage and table size.

The depth percentage - the height of a diamond compared to the stone's diameter - should be approximately 59 percent, according to the American Gem Society standard. If the depth percentage is significantly smaller, then the stone may look too shallow.� If it greatly exceeds that number, then the diamond may look chunky.
The second factor involves the size of the table, which is the flat top of the diamond and is sometimes called its face. The ideal table diameter is 53 to 57 percent of the stone's entire diameter, though stones with a 60 percent figure are considered excellent by many gemologists.� A stone that has a table percentage higher than 64 is likely to lack brilliance and typically takes a steep drop in value.� Similarly, when the table is too small, the diamond may look dark and listless.

Other experts suggest that the crown, or top of the diamond, should be approximately a quarter of the depth, with the bottom pavilion accounting for the rest.

Generally, some gemologists recommend the 60/60 principle: Look for a diamond that has approximately a 60 percent depth percentage and a 60 percent table percentage.

So, what is an ideal cut?
The American Gem Society has a cutting grade system that rates diamonds in 11 categories, ranging from AGS 0 (ideal) to AGS 10 (poor).� Many factors are considered, including the size and symmetry of various facets, the combination of angles and the stone's polish.

Most diamonds are not ideal cuts, because of the skill required and additional work involved.� The majority of diamonds are cut for maximum weight to get the most value out of a rough stone.� Because significant amounts of rough diamond are lost during the making of an ideal cut, cutters forfeit potential earnings when the excess is cut away.� Consequently, ideal-cut diamonds command high prices.

Clarity

Clarity is a measure of the flaws in a diamond.� Every diamond has some sort of a flaw in it.� This is to be expected; diamonds are mined, not manufactured.� The fewer the flaws, more valuable the diamond.� There are several grading systems for clarity.� In the United States, the GIA system is most commonly used.� See the table below.�

G.I.A. Clarity Ratings

Clarity Rating	Definition of Rating
FL (Flawless)	Internal growth lines show no color from the front of the stone.� Minor natural on girdle.� Very small extra facet not visible from front of stone which does not flatten the girdle.
IF	As above, but with minor pits or nicks not in the table, girdle roughness, slight facet abrasion.� Can be removed by polishing the diamond.
VVSI	External faults minimal; internal very tiny spot or group of externally small spots outside the table.� Tiny feather.� Difficult to find using a 10X lens.
VVS2	Only smallest external defects allowed.� Difficult to find using a 10X lens.
VSI	Internal growth lines showing slight color from the front; small cleavages; surface scratches.� Extra facet slightly larger.
VS2	Smallest external blemishes.
SI1	Small internal defects, some external faults.� Slightly larger extra facet, slight cloudy areas and cleavages.
SI2	Small but easily discernible inclusions, some definite external flaws.
I1	Inclusions easily seen with loupe; definite external defects.
I2	Large and numerous inclusions, can be seen with naked eye.
I3	Large and abundant inclusions, very easily seen with naked eye; impaired brilliance.

Carat

Carat refers to the weight of the diamond, not the size.� By definition,�1 carat is exactly 200 milligrams.

Other precious stones are also measured in carats.� Because the density of gemstones varies, a 1-carat diamond will look a different size then a 1-carat topaz.
Since most cut diamonds weigh less then a carat, the carat is subdivided into points.� There are 100 points in a carat.� Since most cut diamonds weigh less then a carat, the carat is subdivided into points.� There are 100 points in a carat.� When you buy a diamond, the weight will be specified in carats, not points (this is required by the Federal Trade Commission.)

Most diamonds sold are under 50 points (one half carat), though diamonds used for engagement rings are usually of higher weight.� .

Don't buy a diamond based on its size alone.� The carat weight is important, but it is just one of many other variables.� Keep in mind that as the size of the diamond increases, the chance of flaws in the stone increases as well.� It's easier to find a smaller diamond with few inclusions than it is a large diamond of the same clarity.� Because of the rarity of large, high-quality diamonds, the prices can be significantly higher for those stones.

Certification

Increasingly, diamonds are accompanied by a certificate, which is a diamond grading report from a major, independent gem laboratory, such as the GIA/Gem Trade Laboratory, EGL (European Gemological Laboratory) or AGL (American Gemological Laboratory).� These certificates contain detailed, unbiased information about a diamond's color, clarity, carat weight, etc

There are advantages to having a certificate for your diamond.� It authenticates the diamond's specifications, ensuring that the diamond is what the salesperson claims it is.� It also offers assurance that the stone is natural and hasn't been treated by an artificial process.� It can be used to prove you own that particular diamond should a dispute arise in the future.� Finally, it can be helpful for insurance purposes if you need to replace it with a stone of comparable value.