Diamonds

"The soul of diamond is the light"
Joseph Joubert

It is difficult to date precisely the moment diamond became known to man. In ancient Egypt diamond was the symbol of the Sun, synonym of strength, courage and truth. It was often placed at the center of the Egyptian cross (ankh), hieroglyphic character meaning life.

Information found in a Sanskrit manuscript show that diamond trade existed as early as the 4th century BC. The Sanskrit word vajra means adamantine, that is, "diamond-like." Earlier still in the 8th century BC, the word "Adamas" appears in Greco-roman text, meaning unconquerable and indestructible is the root word of diamond.

Diamonds were believed to bring luck and strength to their owners, and to protect them against wild beasts, ghosts, evil creatures lurking in the night and even poisons. Hindus believed that diamond was the result of lightning on rocks and used it to make the eyes of certain statue.

The diamond symbolizes wisdom and enlightenment, purity and clarity. It has a harmonizing influence on all the chakras. It is the lucky stone of Leo. Diamond is the birthstone for April.

The quality of a diamond is determined by its Carat, Clarity, Cut, and Color, attributes also known as the "Four C's". It is important to understand how these factors affect the value of the diamond you are considering as it will help you make a confident and sound decision.

Carat

As with other gems, diamond carat is a representation of the weight of the stone; one carat being equivalent to 0.20 grams. A carat is divided into 100 parts, each part being called a point. For example a diamond that weighs one carat also weighs 100 points.

The weight is sometimes described as decimal or fractional parts of a carat. In that case the figure should be accurate to the last decimal place. (i.e.: ".30 carat" could represent a weighs between .295 - .304 carat). Some retailers describe diamond weight in fractions and use the fraction to represent a range of weights. (i.e.: a diamond described as 1/2 carat could weigh between .47 - .54 carat). In any case the retailer should disclose that the weight is not exact, and the reasonable range of weight for each fraction or the weight tolerance being used.

The diamond weight is usually mentioned on the price tag or stamped on the jewelry piece along with the gold quality mark and the trademark.

The table on the left shows a sample of how the different way to measure a diamond weights relate to each other.

Ultimately there is no diamond size better than another. The size of the diamond someone buys is function of his feelings about how important the size is compared to the color, clarity and shape. In the end, when all is said and done, what really count is how the diamond fits in its setting, how much care the jeweler has put in his craft, and how lovely the whole jewelry piece looks to you and your entourage.

Clarity

Every diamond contains a certain number of imperfections called inclusions. These inclusions are part of a diamond's unique personality. The size and quantity of inclusions define the clarity of a diamond and have a great impact on its value, especially if the inclusions interfere with the light passing through it; the value of a diamond decrease as the number and size of the inclusions increase.

The Gemological Institute of America (GIA) developed a clarity grading system which has been used throughout the industry as well as by other diamond grading agencies. The system is based on the observation of a diamond through 10 times magnification (10X) by an expert. If the expert is not able to see any imperfection under 10X magnification, then the diamond is given the maximum rating in the GIA scale: Internally Flawless (IF).

The GIA rating scale is the following:

• Flawless category (FL): no inclusions or blemishes are visible under 10x magnification
• Internally Flawless category (IF): no inclusions visible under 10x magnification, only small blemishes on the diamond surface which can be removed by polishing the stone;
• Very Very Slightly Included (VVS): minute inclusions, difficult for a skilled grader to see under 10x magnification. The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. Pinpoints and needles set the grade at VVS;
• Very Slightly Included category (VS): minor inclusions, relatively easy for a trained grader to see under 10x magnification. The VS category is divided into two grades; VS1 denotes a higher clarity grade than VS2. Typically the inclusions in VS diamonds are invisible without magnification, however infrequently some VS2 inclusions may still be visible to the eye;
• Slightly Included category (SI): noticeable inclusions, easy for a trained grader to see under 10x magnification. The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye;
• Included category (I): obvious inclusions, clearly visible to a trained grader under 10x magnification. In this category diamonds have inclusions usually visible without to the naked eye or that threaten the durability of the stone. This category is divided into three grades; I1 denotes a higher clarity grade than I2, which in turn is higher than I3. Inclusions in I1 category often are seen to the unaided eye. I2 inclusions are easily seen; while I3 diamonds have large and extremely easy to see inclusions that typically impact the brilliance of the diamond, as well as having inclusions that are often likely to threaten the structure of the diamond.

Clarity scales is somewhat subjective: a clarity grade of "slightly included" may represent a different grade on one grading system versus another, depending on the terms used in the scale. Make sure you know how a particular scale and grade represent the clarity of the diamond you're considering.

Cut

In its rough state, a diamond is fairly unremarkable in appearance. Rough diamonds have dull, battered external surfaces often covered by a gummy, opaque skin. The act of polishing a diamond and creating flat facets in symmetrical arrangement brings out the diamond's hidden beauty in an extraordinary fashion. Diamond cut constitutes a more or less symmetrical arrangement of facets which together modify the shape and appearance of a diamond.

The cutter must consider the shape and size of the original stone, when choosing a cut. Two of the most important factors affecting this choice are:

• The refractive index (RI) of the stone, is its capacity to slow light rays traveling through it, and is closely related to its clarity. The RI is fairly high in a diamond, compared to other gems, and is responsible for its brilliance (the amount of incident light reflected back to the viewer);
• The diamond's dispersive power is its ability to split white light into its component basic colors. The flashes of colors, known as fire, emitted by a diamond are a function of the dispersion.

These characteristics are only apparent after the cut, and the art of a cutter consists in obtaining a diamond with as much fire and brilliance as possible without losing too much of the original stone's weigh.

The external brilliance is the light reflected from the surface of a diamond, its luster. Directly related to a diamond's RI, the quality of a finished stone's polish will determine how well a diamond's luster is borne out.

The Internal brilliance is the percentage of incident light reflected back to the viewer from the rear (pavilion) facets, and is a result of the careful consideration of a cut's interfacial angles as they relate to diamond's RI. The goal of the cutter's craft is to attain total internal reflection (TIR: picture on the right), when all incident light is reflected back, by choosing the angle formed by the pavilion facets and girdle plane (crown angle and pavilion angle) such way that the reflected light's, when reaching the pavilion facets, falls outside diamond's critical angle (minimum angle for TIR of 24.4°). Two observations can be made:

• If the pavilion is too shallow, light meets the pavilion facets within the critical angle, and is refracted (i.e., lost) through the pavilion bottom into the air.
• If the pavilion is too deep, light is initially reflected outside the critical angle on one side of the pavilion, but meets the opposite side within the critical angle and is then refracted out the side of the stone.

The scintillation brilliance is the number and arrangement of light reflections from the internal facets. It is the degree of "sparkle" seen when the stone or observer moves. Scintillation is dependent on the size, number, and symmetry of facets, as well as on quality of polish. Very small stones will appear milky if their scintillation is too great, due to the limitations of the human eye, whereas larger stones will appear lifeless if their facets are too large or too few.

The history of diamond cuts can be traced back to the Middle-Ages, while their theoretical basis was not developed until the turn of the 20th century. New technology-notably laser cutting or computer-aided design-has enabled the development of cuts whose complexity, optical performance, and waste reduction were not possible before.

Round brillant 

  Developed around 1900, the round brilliant is the most popular cut given to diamond. It is usually the best choice in terms of salability, insurability (due to its relatively "safe" shape), and desired optics.

The modern round brilliant consists of 58 facets (or 57 if the culet is excluded); 33 on the crown (the top half above the middle or girdle of the stone) and 25 on the pavilion (the lower half below the girdle).

The girdle (the thin band around the crown's base) may be frosted, polished smooth, or faceted. In recent decades, most girdles are faceted; many have 32, 64, 80, or 96 facets; these facets are excluded from the total facet count.

Likewise, some diamonds may have a number of small extra facets on the crown or pavilion that were created to remove surface imperfections during the cutting process. Depending on their size and location, they may negatively impact the symmetry of the cut and are therefore considered during cut grading.

The figure above assumes that the "thick part of the girdle" is the same thickness at all 16 "thick parts". Cutters can tilt or 'index' the upper half (upper girdle) facets. This indexing produces different amounts of weight retention from a given piece of rough and produces different optical performance effects. Indexing can also affect crown height and spread (millimeter footprint versus weight, also called 'weight ratio').

Hearts, Arrows and Fancy cuts

When the table (top facet) is exactly perpendicular to the pavilion (bottom parts) and the other facets precisely aligned with excellent symmetry, a diamond may show patterns that look like arrows from the top and hearts from the bottom. The presence of hearts and arrows property does not always mean the cut will result in the most brilliant diamond. Optimal facet placement is the key to brilliance and more important than facet patterning. Not all ideal round cuts will have the hearts and arrows effect either.

Cutting and polishing a diamond always results in an important loss of weight (rarely less than 50%). Round brilliant cut is preferred when the crystal is an octahedron (8 faces), as often two stones may be cut from one such diamond. Oddly shaped rough diamonds are more likely to be cut in a fancy cut (a cut other round brilliant) which the particular stone shape lends itself to.

The choice of a particular fancy cut is also influenced by fashion; generally speaking, these cuts are not held to the same strict standards as Tolkowsky-derived round brilliants. Most fancy cuts can be grouped into four categories:

• Modified brilliant: the most populous category of fancy cut, because the standard round brilliant can be effectively modified into a wide range of shapes. Because their facet counts and facet arrangements are the same, modified brilliants also look, in terms of brilliance and fire interplay, the most like round brilliants and are therefore, in general and at present, the most saleable. Certain modified round brilliants even exhibit better diamond light performance. The category include the Princess 144, king, High-Light, Magna, marquise or navette, heart, triangular trilliant (also trillian or trillion), oval, and the pear or drop cuts.
• Step cut: with either square or rectangular outlines and with rectilinear facets, arranged parallel to the girdle, these stones often have their corners truncated, creating an emerald cut with an octagonal outline. Instead of a culet, step-cut stones have a keel running the length of the pavilion terminus. Because both the pavilion and crown are comparatively shallow, step cut stones are generally not as bright and never as fiery as brilliant cut stones, but rather accentuate a diamond's clarity (even the slightest flaw would be highly visible) whiteness, and luster. Square step cuts whose corners are not truncated are known as carré. Other forms of the step cut include triangle, kite, lozenge, trapeze, and obus.
• Mixed cut: sharing aspects of both Modified brilliant and Step cuts, it is meant to combine the weight preservation and dimensions of step cut with the optical effects of brilliant. Typically the crown is step-cut and the pavilion brilliant-cut. It is relatively new, with the oldest mixed cut stone dating back to the 1960s. It has been extremely successful commercially and continues to gain popularity, loosening the foothold of the de facto standard round brilliant. Among the first mixed cuts was the Barion cut, Invented by South African diamond cutter Basil Watermeyer in 1971. The Princess cut, first introduced in 1960 by A. Nagy of London, had been the most successful, not only because of its higher fire and brilliance compared to other mixed cuts, but mostly because of all the diamond cuts, it wastes the least of the original stone.
• Rose cuts: in use since the mid 16th century, and derived from older cut, the basic rose cut has a flat base, with no pavilion, and a crown usually composed of 12 or 24 triangular facets in symmetrical arrangement, which rise to form a point. Rose cut stones are usually circular in outline; variations include: the briolette (oval); Antwerp rose (hexagonal); and double Dutch rose (resembling two rose cuts united back-to-back). It is seldom seen nowadays, except in antique jewelry.

Color

Chemically pure and structurally perfect, a diamond is perfectly transparent with no hue, or color. In reality almost no gem-sized natural diamonds is absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal structure.

Depending on its hue and intensity, a diamond's coloration can either detract from or enhance its value. For example, most white diamonds are discounted in price when more yellow hue is detectable, while intense pink or blue diamonds, like as the Hope Diamond, can be dramatically more valuable. Diamonds occur in a restricted variety of colors - steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black. Out of all colored diamonds, red diamonds are the rarest of all.

The Gemological Institute of America (GIA) uses a "D" to "Z" scale it developed for grading the color of "white" (non-fancy colored) diamonds, where "D" is colorless and "Z" is yellow:

• colorless: D, E, F
• near colorless: G, H, I, J (light tint perceptible on the side to perceptible front view)
• faint yellow or brown: K, L, M (easily visible tint front view)
• very light yellow or brown: N, O, P, Q, R
• light yellow or brown: S, T, U, V, W, X, Y, Z

Other diamond grading agencies, notably the European Gemological Laboratory (EGL) and the American Gemological Society (AGS), also use the color scale developed by the GIA.

Diamonds that rate toward the colorless end of the range are sometimes known as "high-color" diamonds, and those toward the other end, "low-color" diamonds. These terms refer to the relative desirability, as demonstrated by market prices, of color grades, not the intensity of the color itself. High-color diamonds are rarer, limiting supply, and their bright white appearance is more desired by consumers, increasing demand, which make them more valuable than low-color diamonds.

Diamonds having a color more intense than "Z" are known as fancy colored diamonds, and are be graded using a system more similar to what is used for other colored gemstones, such as ruby, sapphire, or emerald. When the color is rare, the more intensely colored a diamond is the more valuable it becomes. Fancy-colored diamonds are among the most valuable and sought-after diamonds in the world.

There is 5 degrees of tints for fancy colored diamonds: fancy light, fancy, fancy intense, fancy vivid and fancy deep (i.e.: fancy intense blue diamond).

he purity of Color refers to the hue and the purity of the hue. When considering a fancy color diamond, It's important to take time to understand the vocabulary used to describe the hue you are interested in, the shades available and their relation in terms of rarity and value.

The depth of color refers to the saturation of color combined with the tone, (how "light" or "dark" the color is). Fancy-color diamonds commonly occur in pastel shades. Deep colors such as ruby-red or sapphire-blue are extremely rare and are among the most expensive of all gems.

Depth of color is usually indicated from "faint" to "vivid," "vivid" indicating the richest possible tone in any given color. Stones with a "faint" grade often have such a weak tone that they do not appear to be a "fancy" color at all, but merely a very tinted, off color stone. These should sell for much less than a "light" tone or deeper tones.

The classification pertaining to the depth of color is extremely important. One tonal difference can dramatically affect value. But you must also understand that the terminology and gradations used to indicate the depth of color (the tonal scale) is not the same for every color. To accurately evaluate rarity and value, and to be sure you have found the depth of color that best suits your needs, be sure to find out the specific tonal classifications for the particular color you are considering.

Distribution of the color should be "even" but this is not always the case. Sometimes color occurs in zones, alternating with colorless zones and such stones should be specified as uneven. An uneven stone may appear to have even color distribution when viewed from the top and may be lovely and desirable, but they should cost less than one that has "even" distribution.

Be wary that the color can change so dramatically depending upon the type of light in which it is viewed that it may no longer appear to be the color described on the report at all or may not be one you like.

It's important to understand that in fancy-color diamonds, flawlessness is even rarer than in colorless diamonds. Fancy-color diamonds are often in the SI (slightly included) range; I1-I3 (imperfect) grades are also common. In the fancy colors, however, SI and I grades don't carry the stigma associated with these grades in colorless diamonds, especially if the stone has a rare or unusually deep color. This is not to say there are no "flawless" fancy-color diamonds or diamonds in the rarer clarity grades. But if the color is rare, and the diamond also has a high clarity grade, the cost will be disproportionately much higher.

Some diamonds exhibit fluorescence of various colors and intensities under long wave (LW) ultra-violet light. In the majority of the cases, this fluorescence is of blue color. A slight fluorescence depreciates diamonds D, E, and F. A slight fluorescence gives an increase in value to diamonds equal or below G.

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The Rapaport Diamond Report

Established in 1978, the Rapaport Diamond Report is the primary source of diamond pricing and market information for the diamond industry. Available for professionals on subscription, it is the international standard used to establish prices in all the major markets. The Report also provides the latest news, global market reports and the best in-depth analysis of the diamond markets. The Report lists specific stones for sale with price and cut information.

Since prices are base on asking price level, they are higher than actual dealer transaction prices, which are often quoted at discount to the Report. Prices are indicated for Round, Pear, Marquise, and Princess, shapes, and organized by size (from one fifth to 5.99 carats), color and clarity. Because cut/shape, fluorescence, symmetry and polish are not included on the list there can be important variations in price.

Diamond prices indicated on these lists are expressed per carat, in hundredth of American dollar ($100's per carat).

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Some diamonds may be treated to improve the appearance of natural, and sometimes synthetic, diamond in similar ways as other gemstones. As these treatments improve the clarity of the diamond, some jewelers refer to them as clarity enhancement.

The range of treatments include clarity enhancement treatments such as laser drilling to remove inclusions, application of sealants to fill cracks, and color enhancement treatments to improve a white diamond's color grade, and treatments to give fancy color to a white or off-color diamond.

Clarity enhancement

The clarity or purity of a diamond, the relative or apparent severity of flaws within the stone, has, like the other "four Cs", a strong bearing on the evaluation of a diamond's worth. The most common flaws or inclusions seen in diamond are fractures, commonly called feathers due to their feathery whitish appearance, and solid foreign crystals within the diamond. Some sellers sometimes choose to reduce the visual impact of inclusions through one or more of a variety of treatments.

Laser drilling involves the use of a laser beam on a diamond that has black inclusions or spots. A laser beam is aimed at the inclusion to drill very tiny holes (less than 0.2 millimeters or 0.005 inches). Acid is then forced through the tunnel made by the laser beam to remove the inclusion (or significantly reduce its visibility). The treatment is permanent and the stone does not require special care afterward.

While a laser-drilled diamond may appear as beautiful as a comparable untreated stone, it may not be as valuable, because an untreated stone of the same quality is rarer and therefore more valuable. Under microscopic inspection the fine bore holes are readily detectable. Jewelers have an obligation to tell you whether the diamond you're considering has been laser-drilled.

Fracture filling conceals cracks in diamonds by filling them with specially-formulated glasses with a refractive index (RI) approximating that of diamond. The glass filling of diamond often follows the laser drilling and acid-etching of inclusions, though if the fractures are surface-reaching, no drilling may be required.

The glass present in fracture-filled diamonds can usually be detected by a trained gemologist under the microscope. The most obvious signs are the surface-reaching bore holes and fractures and the so-called "flash effect", which refers to the bright flashes of color seen when a fracture-filled diamond is rotated (from an electric blue or purple to an orange or yellow).

The fracture-filling of diamond is a controversial treatment within the industry, and increasingly among the public as well, due to its radical and impermanent nature. The filling glass melts at such a low temperature that it easily "sweats" out of a diamond under the heat of a jeweler's torch; thus routine jewelry repair can lead to a complete degradation of clarity or in some cases shattering, especially if the jeweler is not aware of the treatment. Similarly, a fracture-filled diamond placed in an ultrasonic cleaner may not survive intact. Jewelers also have an obligation to tell you if the diamond you're considering has been fracture-filled.

Color enhancements

Diamonds can be transformed by treatments into beautiful, desirable colors using several techniques.

Irradiation

Nowadays diamond is safely irradiated producing shades of green, black, or blue. Bright shades of yellow, orange, brown, or pink can be obtained using annealing techniques (allow some of the lattice defects created during irradiation to be corrected).

Indication of treatment can be detected in gemological laboratories using spectrophotometers (a device for measuring light intensity as a function of the color, or more specifically, the wavelength of light). The stone is cooled to very low temperatures (below -150°C) to improve detection.

Coatings

The application of colored tin foil to the pavilion (bottom) surfaces of gemstones was common practice during Georgian and Victorian era. This was the first treatment, aside from cutting and polishing, applied to diamond. Foiled diamonds are mounted in closed-back jewelry settings, which may make their detection problematic. Under magnification, areas where the foil has flaked or lifted away are often seen; moisture that has entered between the stone and foil will also cause degradation and uneven color. Because of its antique status, the presence of foiled diamonds in older jewelry will not detract from its value.

Modern and more sophisticated surface coatings methods have been developed: these include violet-blue dyes and vacuum-sputtered films. These coatings effectively whiten the apparent color of a yellow-tinted diamond, because the two colors are complementary and act to cancel each other out. Usually only applied to the pavilion or girdle region of a diamond, these coatings are among the hardest treatments to detect.

While the dyes may be removed in hot water or alcohol with ease, the vacuum-sputtered films require a dip in sulfuric acid to remove. The films can be detected under high magnification by the presence of raised areas where air bubbles are trapped, and by worn areas where the coating has been scratched off. These treatments are considered fraudulent unless disclosed.

Another coating treatment applies a thin film of synthetic diamond to the surface of a diamond simulant. This gives the simulated diamond certain characteristics of real diamond, including higher resistance to wear and scratching, higher thermal conductivity, and lower electrical conductivity. While resistance to wear is a legitimate goal of this technique, some employ it in order to make diamond simulants more difficult to detect through conventional means, which may be fraudulent if they are attempting to represent a simulated diamond as real.

High-pressure, high-temperature processes (HPHT)

A new technique known as "high-pressure, high-temperature annealing" is being used now to transform very off-white and brownish diamonds into "colorless" and "near colorless" stones. The technique is also used to transform these diamonds into a variety of "fancy" colors, from light yellow, greenish yellow or yellowish green to exquisite shades of pink and blue. While the yellowish green and greenish yellow diamonds often have a distinctive look that sets them apart from most diamonds of comparable natural color, this is not the case with pink and blue, which are very difficult to distinguish from the natural.

Diamonds treated to remove their color by General Electric are given laser inscriptions on their girdles: these inscriptions read "GE POL", with "POL" standing for Pegasus Overseas Ltd, a partnered firm. It is possible to polish this inscription away, so its absence cannot be a trusted sign of natural color. Although it is permanent, HTHP treatment should be disclosed to the buyer at the time of sale.

A diamond, whose color was modified artificially, must be mentioned in section "Comments" on its certificate. You will find these terms "Color enhanced".

It is important to know whether the color of a fancy colored diamond is natural or the result of a treatment so you know you have paid an appropriate price. Definitive identification of HTHP processed stones is left to well-equipped gemological laboratories.

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