What are diamonds ?

Natural diamonds are pure carbon, formed into crystals deep below the earth’s crust many millions of years ago. Diamonds are found and mined in several parts of the world but predominantly in southern Africa where flows of volcanic lava, known as Kimberlite, have carried diamond deposits to the surface. These deposits can be mined or quarried to recover the diamonds within the Kimberlite. As the hardest natural substance known to man, diamonds brought to the surface in this way have survived the effects of geological erosion, often being washed down river valleys and into the sea. Diamonds can therefore be recovered from the alluvial deposits in rivers as well as from the sea bed and even from beaches. In their recovered or “rough” form they are far from the cut and polished gemstones which we prize today. Rough diamonds have to be sorted and graded before those which can be used for jewellery are shipped to specialist cutting and polishing centres around the world. Diamonds not suitable for jewellery are used for industrial cutting and drilling.

Diamond Color

The Diamond Color Scale
The color scale runs the alphabet from D - colorless to Z - light yellow, brown, or gray color. D is the rarest color and thus the most valuable.
Diamonds most often form in nature with nitrogen impurities in their atomic structure.
This causes them to show a subtle tint of yellow color. As you move down the color scale the diamonds become more yellow (or brown or gray) and thus less valuable.
D-E-F Group: Colorless
This diamond group is the rarest and most expensive. They are common enough to be found in many stores, but still command the highest prices. They show virtually no color.
G-H-I Group: Near Colorless
This is a very popular color group because of its lower price, yet they still possess high enough color to face up reasonably white in a mounting. Diamonds in the lower end of this group show a very light shade of color and may present themselves better in a yellow gold setting, rather than in white or platinum.
J-K-L-M: Faint Yellow
This is the group that begins to show slight yellow color.Slight color may be noticeable from the top of the stone, but probably more from the sides.
N through R: Very light Yellow
Diamonds in the N-R group show yellow color even when mounted in jewelry. Determining the exact color of a diamond in this group is less important due to the fact that their prices are similar. Certificates for diamonds in the N-R group are less common because of their relatively low price.
S through Z: Light yellow
Diamonds in this group show substantial color when loose or mounted.
Fancy Colored Diamonds
Fancy Yellow diamonds can command prices as high as D colors or more. Colors below the Z range are considered to have color as an asset and are graded into the fancy color range. The fancy color ranges are as follows: Fancy Light - Fancy - Fancy Intense - Fancy Deep - and Fancy Vivid. While Fancy Yellow is more common, Fancy Colored Diamonds can and do occur in every possible color. Often the color is described with a secondary mixed color preceding it.
Ex: Fancy Intense Orangy-Yellow, with yellow, the second color mentioned, being the predominant color.
So, to summarize, there are Colorless Diamonds (D, E, F), Near Colorless Diamonds (G,H,I), progressively off colored diamonds (J-Z), being yellow, brown, or gray, and Fancy Colored Diamonds. Fancy Colored Diamonds are not always "Natural". Their color may have been modified or enhanced through one or more processes involving irradiation and/or extreme heat. While this enhancement may in fact be permanent, the occurrence of natural color in diamond is far more rare and thus more expensive. The tests for identification of "origin of color" are usually conclusive, but may require sophisticated equipment and extremely qualified testers. It is highly recommended to have the G.I.A. confirm the origin of color, as natural, in any fancy colored diamond of enough size to warrant it.

The Brown Color Group

Brown diamonds have a tint of brownish body color. The brown group is usually less expensive than any other group due to the fact that they are less appealing to most consumers. In their lightest tones, they face up reasonably white in a yellow setting. These stones are often described as "TLB" or Top Light Brown. The brown group is graded by tone, from light to dark in much the same way as other diamonds, however their appearance may be slightly whiter than a diamond of slightly yellowish body color, in the same color grade range. Establishing the correct value with regard to significantly brown diamonds is difficult. The Argyle mines in Australia produce a significant quantity of brown diamonds, and have successfully marketed them using the descriptive names, "cognac" and "champagne".
The common shades are:
Very light brown (champagne), medium brown (champagne), Brown (dark champagne), and Dark brown (fancy cognac). A color scale has been devised by the Argyle Mines of Australia for use in grading these diamonds using C1 - C7 grades to separate them into their progressively darker tonal ranges.

In spite of the significant marketing efforts of the Argyle Mines, demand for the brown diamonds is not great and they generally command relatively low prices.

Fluorescence

Fluorescence is a phenomenon which causes some diamonds to glow under ultra violet light (UV), which is abundant in natural daylight and some artificial lighting.
The following are the possible grades given to fluorescence:
Faint, Medium, Strong, Very Strong
All grading reports denote the diamond’s fluorescence as well as color. It is estimated that 20%-25% of all diamonds have some degree of fluorescence. Most often diamonds will fluoresce blue, but occasionally yellow or green or an unusual color may occur.
Strong fluorescence can cause a diamond to look hazy or less transparent, however this is not always the case. Years ago the term "blue white" was used to describe the finest of diamonds, many of which had bluish overtones caused by fluorescence. Unfortunately the term became misused and seldom accompanied a diamond that was truly white or blue. It is not appropriate to use the expression in modern times unless the diamond truly possesses a bluish hue.
Generally speaking, a diamond with strong fluorescence, sometimes called an over-blue, which diminishes it's brilliance and gives it a sleepy, or greasy appearance, will cost less than one with faint or no fluorescence. If a diamond is lightly tinted and has faint to moderate fluorescence, it may face up whiter than another diamond of similar lightly tinted color possessing no fluorescence, and may actually cost more.

Diamond Clarity

This chart represents the plotting of clarity characteristics as they may appear on a Grading Report from an Independent Lab, such as the Gemological Institute of America, the Jewelry Industry's foremost leader in Education and Evaluation of diamonds and colored stones. Generally, internal characteristics are plotted in red and external (surface) characteristics in green. The plotting is generally "exaggerated" in size to reflect the "nature" of the characteristics, and not the relative size. Even inclusions which are difficult to see under 10x magnification may appear quite large on the plot, in order to accurately describe the type of characteristic to anyone viewing the stone and the report. Please be warned, the enlarged chart is very large and may take a while to open with a slow modem.

IF - INTERNALLY FLAWLESS - describes diamonds which have no internal characteristics observable under 10x magnification, the same conditions as (FL), but which have minor surface blemishes that do not penetrate the stone. These stones are potentially flawless if they underwent additional finishing.
VVS1 & VVS2 - VERY, VERY SLIGHTLY INCLUDED - describes diamonds that have very, very small inclusions which are difficult for a gemologist to see at 10x magnification.
VS1 & VS2 - VERY SLIGHTLY INCLUDED - describes diamonds with very small inclusions which can be difficult to observe with 10x magnification. Inclusions are not visible to the unaided eye, except on larger stones or occasionally with Emerald Cut diamonds.
SI1 & SI2 - SLIGHTLY INCLUDED - describes diamonds with small inclusions which are usually obvious when viewed with 10x magnification. Inclusions are difficult to see with the unaided eye, except on larger stones or occasionally with Emerald Cut diamonds. Generally SI1 graded stones are eye clean, while SI2 graded stones may or may not be eye clean.
I1, I2, & I3 - IMPERFECT - describes diamonds with medium to large inclusions (Piques) which are usually obvious to a gemologist with the unaided eye. An I1 may have an inclusion located to the side while an I2 will have it centrally located or numerous inclusions.

Diamond Cut

The various parts of a diamond are illustrated to the right and below.

The typical faceting style and facet names for the Round Brilliant Cut are illustrated here. Counting the culet, which is not always actually polished as a facet, the Round Brilliant has 58 facets. Their exact placement relative to one another, as well as the proper angles of their placement, plays a critical role in the appearance of the finished stone.
Any diamond which is not "poorly cut" will reflect some of the light which enters it and disperse some of it, which gives diamonds their unique brilliance and dispersion. The primary reason for grinding and polishing facets on a diamond is to enable the light to enter the stone and reflect back to the viewer in a positive way, thus making the given stone "marketable". Unfortunately, economics plays a role in the decision making which directs the size and placement of the facets as well as the ultimate size and shape of the finished stone.

Ideal Cut

Many years ago, the "ideal" proportions of a round brilliant cut were mathematically computed. While these proportions will generate a diamond with not only the maximum reflection of light, they also render the ideal balance of brilliance (reflected white light) and dispersion (refracted spectral colors). Unfortunately, the maximum potential weight recovery from the rough is sacrificed. Modern day diamond cutters attempt to balance these factors and will most frequently allow popular weight categories that are targeted as well as increased yield to direct their cutting decisions.

A diamond which has been cut too shallow will not only reflect less light, but the lessening of the angles of the pavilion facets will also make the stone "window" or show a see through effect. This appears to the eye as if there were dead space instead of sparkle. These diamonds will also often show an internal reflection of the top of the stone in the bottom, which resembles a dark circle or "fish-eye".

A diamond that has been cut too deep will generally appear dark through the center. This occurs because the light is "leaking" through the back of the stone instead of reflecting back to the eye through the top. Add to this, the fact that the diameter of the stone, or it's apparent size, is minimized and you have a smaller facing stone than it's weight would usually render.

The Ideal Cut, which is illustrated below requires exact placement of facets at exact angles relative to one another. They are generally available to a discerning buyer at a premium over all other diamonds in their class.

A Premium Cut diamond demonstrates subtle variations from the Ideal Cut. Although these differences do affect the reflection of light, a Premium Cut still achieves a harmonious balance between it's proportions and the display of brilliance and dispersion.