The most familiar usage of diamonds today is as gemstones used for
adornment—a usage which dates back into
antiquity. The
dispersion of white light into
spectral colors is the primary gemological characteristic of gem diamonds. In the twentieth century,
gemologists have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics known informally as the "four Cs" are now commonly used as the basic descriptors of diamonds: carat, cut, color, and clarity. This system was developed by
Gemological Institute of America in 1953 as internationally recognized standard to evaluate diamonds' characteristics. Most gem diamonds are traded on the wholesale market based on single values for each of the four Cs; for example knowing that a diamond is rated as , VS2 clarity, F color, excellent cut round brilliant, is enough to reasonably establish an expected price range. More detailed information from within each characteristic is used to determine actual market value for individual stones. Consumers who purchase individual diamonds are often advised to use the four Cs to pick the diamond that is "right" for them. Other characteristics also influence the value and appearance of a gem diamond. These include physical characteristics such as the presence of
fluorescence as well as the diamond's source and which gemological institute evaluated the diamond.
Cleanliness also dramatically affects a diamond's beauty. There are two major non-profit gemological associations which grade and provide reports, (informally referred to by the term
certificate or
cert, which is a
misnomer for many grading reports) on diamonds; while carat weight and cut angles are mathematically defined, the clarity and color are judged by the trained human eye and are therefore open to slight variance in interpretation. These associations are listed below. •
Gemological Institute of America (GIA) was the first laboratory in America to issue modern diamond reports, and is held in high regard amongst gemologists for its consistent, conservative grading. • Diamond High Council (HRD) Official certification laboratory of the Belgian diamond industry, located in
Antwerp. Within the last two decades, a number of for-profit gemological grading laboratories have also been established, many of them also based in Antwerp or New York. These entities serve to provide similar services as the non-profit associations above, but in a less expensive and more timely fashion. They produce certificates that are similar to those of the GIA.
Weight The
carat weight measures the mass of a diamond. One carat is defined as 200
milligrams (about 0.007
ounces
avoirdupois). The
point unit—equal to one one-hundredth of a carat (0.01 carat, or 2 mg)—is commonly used for diamonds of less than one carat. All else being equal, the price per carat increases with carat weight, since larger diamonds are both rarer and more desirable for use as gemstones. The price per carat does not increase
linearly (proportionally) with increasing size. Instead, there are sharp jumps around milestone carat weights, as demand is much higher for diamonds weighing just more than a milestone than for those weighing just less. As an example, a 0.99-carat diamond may have a significantly lower price per carat than a comparable 1.01-carat diamond, because of differences in demand. A weekly
diamond price list, the
Rapaport Diamond Report is published by
Martin Rapaport, CEO of Rapaport Group of New York, for different diamond cuts, clarity and weights. It is considered the
de facto retail price baseline. Jewelers often trade diamonds at negotiated discounts off the Rapaport price (e.g., "R −3%"). In the wholesale trade of gem diamonds, carat is often used in denominating lots of diamonds for sale. For example, a buyer may place an order for of , D–F, VS2-SI1, excellent cut diamonds, indicating a wish to purchase 200 diamonds ( total mass) of those approximate characteristics. Because of this, diamond prices (particularly among wholesalers and other industry professionals) are often quoted per carat, rather than per stone.
Total carat weight (t.c.w.) is a phrase used to describe the total mass of diamonds or other gemstone in a piece of jewelry, when more than one gemstone is used. Diamond solitaire earrings, for example, are usually quoted in t.c.w. when placed for sale, indicating the mass of the diamonds in both earrings and not each individual diamond. T.c.w. is also widely used for diamond necklaces, bracelets and other similar jewelry pieces.
Clarity Clarity is a measure of internal defects of a diamond called
inclusions. Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. The
Gemological Institute of America (GIA) and other organizations have developed systems to grade clarity, which are based on those inclusions which are visible to a trained professional when a diamond is viewed under 10× magnification. Diamonds become increasingly rare when considering higher clarity gradings. Only about 20% of all diamonds mined have a clarity rating high enough for the diamond to be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use. Of that top 20%, a significant portion contains one or more visible inclusions. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. When set in jewelry, it may also be possible to hide certain inclusion behind mounting hardware such as prongs in a way that renders the defect invisible. However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may increase the likelihood of a fracture. Diamonds are graded by the major societies on a scale ranging from flawless to imperfect.
Color Diamond The finest quality as per color grading is totally colorless, which is graded as D color diamond across the globe, meaning it is absolutely free from any color. The next grade has a very slight trace of color, which can be observed by any expert diamond valuer/grading laboratory. However, when studded in jewellery these very light colored diamonds do not show any color or it is not possible to make out color shades. These are graded as E color or F color diamonds. Diamonds which show very little traces of color are graded as G or H color diamonds. Slightly colored diamonds are graded as I or J or K color. A diamond can be found in any color in addition to colorless. Some of the colored diamonds, such as pink, are very rare. A chemically pure and structurally perfect diamond is perfectly transparent with no
hue, or
color. However, in reality most gem-sized natural diamonds are imperfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the
crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price as a more yellow hue is detectable, while intense pink or blue diamonds (such as the
Hope Diamond) can be dramatically more valuable. The
Aurora Diamond Collection displays a spectacular array of naturally
colored diamonds, which occur in every color of the rainbow. Most diamonds used as gemstones are basically transparent with little tint, or
white diamonds. The most common impurity,
nitrogen, replaces a small proportion of carbon atoms in a diamond's structure and causes a yellowish to brownish tint. This effect is present in almost all white diamonds; in only the rarest diamonds is the coloration from this effect undetectable. The GIA has developed a rating system for color in white diamonds, from D to Z (with D being "colorless" and Z having a bright yellow coloration), which has been widely adopted in the industry and is universally recognized, superseding several older systems. The
GIA system uses a benchmark set of natural diamonds of known color grade, along with standardized and carefully controlled lighting conditions. Diamonds with higher color grades are rarer, in higher demand, and therefore more expensive, than lower color grades. Oddly enough, diamonds graded Z are also rare, and the bright yellow color is also highly valued. Diamonds graded D–F are considered "colorless", G–J are considered "near-colorless", K–M are "slightly colored". N–Y usually appears light yellow or brown. In contrast to yellow or brown hues, diamonds of other colors are more rare and valuable. While even a pale pink or blue hue may increase the value of a diamond, more intense coloration is usually considered more desirable and commands the highest prices. A variety of impurities and structural imperfections cause different colors in diamonds, including yellow, pink, blue, red, green, brown, and other hues. There is also a kind of pebble containing
polycrystalline diamond that is black or gray, called
carbonado, which may be of extraterrestrial origin. It is the toughest form of diamond and is used as an
abrasive, though sometimes also as precious stone (for example
The Enigma &
The Black Falcon). Diamonds with unusual or intense coloration are sometimes labeled "fancy" in the diamond industry. Intense yellow coloration is considered one of the fancy colors, and is separate from the color grades of white diamonds. Gemologists have developed rating systems for fancy colored diamonds, but they are not in common use because of the relative rarity of such diamonds.
Cut Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The
cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions. The cut of a diamond describes the quality of workmanship and the angles to which a diamond is cut. Often
diamond cut is confused with "shape". There are mathematical guidelines for the angles and length ratios at which the diamond is supposed to be cut in order to reflect the maximum amount of light. Round brilliant diamonds, the most common, are guided by these specific guidelines, though fancy cut stones are not able to be as accurately guided by mathematical specifics. The techniques for cutting diamonds have been developed over hundreds of years, with perhaps the greatest achievements made in 1919 by
mathematician and gem enthusiast
Marcel Tolkowsky. He developed the
round brilliant cut by calculating the ideal shape to return and scatter light when a diamond is viewed from above. The modern round brilliant has 57 facets (polished faces), counting 33 on the
crown (the top half), and 24 on the
pavilion (the lower half). The girdle is the thin middle part. The function of the crown is to refract light into various colors, and the pavilion's function is to reflect light back through the top of the diamond. Tolkowsky's calculations included some approximations. He calculated the ideal dimensions as: • Table percentage (corner-to-corner diameter of the table divided by overall diameter) = 53% • Depth percentage (overall depth divided by overall diameter) = 59.3% (not including adjustments for the culet height and girdle thickness) • Pavilion angle (angle between the girdle and the pavilion main facets) = 40.75° • Crown angle (angle between the girdle and the crown's kite facets) = 34.5° • Pavilion depth (depth of pavilion divided by overall diameter) = 43.1% • Crown depth (depth of crown divided by overall diameter) = 16.2% The culet is the tiny point or facet at the bottom of the diamond. This should be a negligible diameter, otherwise light leaks out of the bottom. Tolkowsky's calculations included neither a culet nor a girdle. However, a girdle is required in reality in order to prevent the diamond from easily chipping in the setting. The thick part of the girdle is normally about 1.7% (of the overall diameter) thicker than the thin part of the girdle. Proponents of these machines argue they help sellers demonstrate the light performance of the diamond in addition to the traditional 4 Cs. Detractors, however, see these machines as marketing tools rather than scientific ones. The GIA has developed a set of criteria for grading the cut of round brilliant stones that is now the standard in the diamond industry and is called Facetware.
Process , at a 2001 diamond exhibition in Paris. An uncut diamond does not show its prized optical properties. The process of shaping a rough diamond into a polished gemstone is both an art and a science. The choice of cut is often decided by the original shape of the rough stone, location of the inclusions and flaws to be eliminated, the preservation of the weight, popularity of certain shapes amongst consumers and many other considerations. The round brilliant cut is preferred when the crystal is an octahedron, as often two stones may be cut from one such crystal. Oddly shaped crystals such as macles are more likely to be cut in a
fancy cut—that is, a cut other than the round brilliant—which the particular crystal shape lends itself to. Even with modern techniques, the cutting and polishing of a diamond crystal always results in a dramatic loss of weight; rarely is it less than 50%. Sometimes the cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions or to preserve the carat rating. Since the per carat price of diamond shifts around key milestones (such as ), many one-carat diamonds are the result of compromising cut for carat. Some jewelry experts advise consumers to buy a diamond for its better price or buy a diamond for its better cut, avoiding a diamond which is more likely to be a poorly cut stone.
Light performance In the gem trade, the term light performance is used to describe how well a polished diamond will return light to the viewer. There are three light properties which are described in relation to light performance: brilliance, fire, and scintillation. Brilliance refers to the white light reflections from the external and internal facet surfaces. Fire refers to the spectral colors which are produced as a result of the diamond dispersing the white light. Scintillation refers to the small flashes of light that are seen when the diamond, light source or the viewer is moved. A diamond that is cut and polished to produce a high level of these qualities is said to be high in
light performance. The setting diamonds are placed in also affect the performance of light through a diamond. The three most commonly used settings are: Prong, Bezel, and Channel. Prong settings are the most popular setting for diamond jewelry. The prong setting consists of four or six 'claws' that cradle the diamond, allowing the maximum amount of light to enter from all angles, allowing the diamonds to appear larger and more brilliant. In bezel settings the diamond or gemstone is completely surrounded by a rim of metal, which can be molded into any shape to accommodate the stone. Used to set earrings, necklaces, bracelets, and rings, bezel settings can have open or closed backs, and generally can be molded to allow a lot of light to pass through. Channel settings set the stones right next to each other with no metal separating them. This setting is mostly used in wedding and anniversary bands. The outer ridge is then worked over the edges of the stones to create a smooth exterior surface. This also protects the girdle area of the stone.
Fluorescence About a third of all diamonds will glow under
ultraviolet light, usually a blue color, which may be noticeable under a
black light or strong
sunlight. According to the
GIA, who reviewed a
random sample of 26,010 natural diamonds, 65% of the diamonds in the sample did not
fluoresce. Of the 35% that did fluoresce, 97% had
blue fluorescence of which 38% had faint blue fluorescence and 62% had fluorescence that ranged from medium to very strong blue. Other colors diamonds can fluoresce are
green,
yellow, and
red, but are very rare and are sometimes a combination of the colors such as
blue-green or
orange. In October 2020, a population of diamonds were discovered within an alluvial deposit at the Ellendale diamond field in Australia that exhibit an ultra rare purple fluorescence. Some diamonds with "very strong" fluorescence can have a "milky" or "oily" look to them, but they are also very rare and are termed "over-blues." Their study concluded that with the exception of "over-blues" and yellow fluorescent diamonds, fluorescence had little effect on transparency and that the strong and very strong blue fluorescent diamonds on average had better color appearance than non-fluorescent stones. Since blue is a
complementary color to yellow and so can appear to cancel it out, strong blue fluorescence had especially better color appearance with lower color graded diamonds that have a slight yellowish tint, such as I or J color, but had little effect on the more colorless D, E, and F color grades.
Trade History Before the diamond industry standardized to the GIA grading terminology the term "Blue White" (Blauweiss) was widely used to describe the most highly regarded white diamonds. The term described colorless diamonds with a tinge of blue fluorescence. These stones were actively sought by merchants thanks to their appealing ‘ice’ effect and consumers paid higher prices for diamonds with fluorescence. Quality retailers such as C. D. Peacock of Chicago Il. made their name selling genuine Blue-White diamonds, but others in the industry saw the opportunity to use the term to sell lower quality diamonds. By 1938, the term "Blue White" and the underlying concept that blue (i.e. fluorescence) added value to white (colorless) diamonds had become abused by too many unscrupulous dealers and the U.S. Federal Trade Commission outlawed the use of the term Blue White. The subsequent FTC restrictions undoubtedly encouraged the establishment of today's GIA color grading system. The new GIA grading system had no place for the effect of fluorescence on color and the desirability of fluorescence in a diamond began to wane in the years that followed. Diamonds with fluorescence were marked down in price. Ironically, in 1997, a seminal study by the
Gemological Institute of America (GIA) concluded that, "in general, the strength of fluorescence had no widely perceptible effect on the color appearance of diamonds viewed table-down (as is typical in laboratory and trade grading). In the table-up position (as is commonly encountered in jewellery stores), diamonds described as strongly or very strongly fluorescent were, on average, reported as having a better color appearance than less fluorescent stones". The GIA study concluded that "the diamond industry would be better served by considering each individual diamond on its own visual merits." Today, fluorescent natural diamonds are again becoming very desirable with major diamond miners such as the world's largest diamond producer, Alrosa, reminding the industry of the historic desirability and beauty of naturally fluorescent diamonds.
Cleaning Cleanliness significantly affects a diamond's beauty. A clean diamond is more brilliant and fiery than the same diamond when it is "dirty". Dirt or grease on the top of a diamond reduces its luster. Water, dirt, or grease on the bottom of a diamond interferes with the diamond's brilliance and fire. Even a thin film absorbs some light that could have been reflected to the viewer. Colored dye or smudges can affect the perceived color of a diamond. Historically, some jewelers' stones were misgraded because of smudges on the girdle, or dye on the culet. Current practice is to clean a diamond thoroughly before grading its color. Maintaining a clean diamond can sometimes be difficult as jewelry settings can obstruct cleaning, and oils, grease, and other
hydrophobic materials adhere well to a diamond. Furthermore, the intricate facets of certain diamond cuts may trap dirt and grime, requiring specialized cleaning techniques. Many jewelers use
steam cleaners. Some jewelers provide their customers with
ammonia-based cleaning kits;
ultrasonic cleaners are also popular. ==Value==