Buyer's Guide: Diamonds

Diamonds are the hardest of all gemstones and the hardest transparent substance. Natural diamonds are found in kimberlite or lamproite pipes produced by volcanic magma millions of years ago. Diamonds are a simple crystalline structure of carbon produced by extremely high pressure and temperature. The melting point of a diamond is 4,000 degree C or about 2.5 times higher than the melting point of steel. Gem quality diamonds are rare; this helps to account for their value.

A rough diamond resembles a common pebble; but when properly cut and polished by a skilled diamond cutter, its "fire" or brilliance comes to life. Fire can be a seen as a flash, spark, sparkle, or animation of light and color caused by the proportioning, angles and positioning of facets that reflect and refract light inside the diamond. Facets must be precisely cut so that light bounces freely inside the diamond, and then exits through the crown or top, directly to the eye of the viewer. The table, top or crown facet is the largest and most important facet on a diamond.

It takes from several hours to several months to cut and polish a diamond, depending on the size, shape and style of the final product. During cutting and polishing, a rough diamond will lose approximately 50% of its original weight.

The most popular shape for cut diamonds is the round or round brilliant . Other popular shapes are the oval, square, marquise, pear, emerald, heart and princess.

People attribute a variety of qualities to diamonds: strength, character, wealth, success, beauty, purity, eternity ("a diamond is forever"), endurance, milestones, romance, engagement and love.

Diamond Cutting

The cut gives each diamond its unique sparkle and brilliance by allowing the maximum amount of light to enter and reflect back out of the diamond. A well-cut diamond will be considerably more beautiful and valuable than a poorly cut stone of the same size, clarity, and color.

There are six diamond shapes: round brilliant-cut, marquise, emerald-cut, pear-shaped, oval and heart-shaped. More than 75% of all diamonds sold are round stones. The solitaire, a single round diamond prong-set in platinum or gold, epitomizes the American engagement ring.

How Quality is Determined

Four factors are used to evaluate diamonds:

Carat weight - one carat equals 0.2 grams. One carat equals 100 points. A 50 point diamond is described as .50 carats.

Cut - The arrangement of a diamond's facets. This is the only one of the four factors under the direct control of man. Facets are planned and proportioned so that ambient light is reflected from one facet to another until the light exits from the top or crown of the diamond. "Symmetry" refers to how well the facets line up with each other. Grading standards used by the Gemological Institute of America (GIA) for "cut" are: Excellent, Very Good, Good, Fair and Poor.

Clarity - The degree to which a diamond is free from natural phenomena known as inclusions: impurities, non-crystallized carbon, cracks or scratches. Most inclusions can only be seen under magnification. GIA grading standards for clarity are:

• Flawless (FI): Flawless diamonds show no blemishes or inclusions when examined under 10x magnification

• Internally Flawless (IF): Stones show no inclusions and only insignificant blemishes under 10x magnification.

• Very Very Slightly Included (VVS₁ and VVS₂): VVS diamonds contain minute inclusions that are difficult for even a skilled grader to locate under 10x magnification. In VVS₁, they are extremely difficult to see, visible only from the pavilion, or small and shallow enough to be removed by minor repolishing. In VVS₂, they are very difficult to see.

• Very Slightly Included (VS₁ and VS₂): VS diamonds contain minor inclusions ranging from difficult (VS₁) to somewhat easy (VS₂) to see under 10x magnification.

• Slightly Included (SI₁ and SI₂): SI stones contain noticeable inclusions which are easy (SI₁) or very easy (SI₂) to see under 10x magnification. These diamonds are sometimes called "eye clean" because they appear flawless to the naked eye.

• Imperfect (I₁, I₂, and I₃): I-grade diamonds contain inclusions which are obvious under 10x magnification, and can usually be seen with the unaided eye. These flaws can seriously affect the stone's potential durability, or are so numerous they affect the transparency and brilliance of the stone.

Color

If you are looking for a diamond for an engagement ring, earrings or pendant, find one that is the whitest white. Of the Four Cs of diamond valuation, many experts name color as the number one consideration. Diamond colors are graded on a simple system, beginning with "D" for colorless and move down the alphabet to stones with traces of color to stones with visible shadings. Stones with poor color can be found towards the end of the alphabet.

A diamond's ability to reflect and refract light is dependent on its whiteness. When white light enters the diamond, part of the ray is reflected back to the observer's eye, but the rest of the light penetrates the stone. Refraction occurs when the ray is deflected toward the center of the stone, then bounced back to the surface. The whiter the color, the greater the reaction.

Since color differences can be so subtle, they are impossible to determine by the untrained eye. To grade a diamond, gemologists often place it on a white background next to another diamond that has been previously graded.

GIA's grading standards begin with D (colorless) and go to Z (light yellow). The value of a diamond decreases as the scale moves from D to Z. Grades of D to H are preferred for fine jewelry.

Summary:

The market value of a diamond is linked to a combination of these four factors. Hundreds of combinations are possible. The current trend of consumers is to give high priority to color , then to clarity, next to cut and finally to carat weight. Some demand is also being created for naturally occurring "fancy" color diamonds.