THE 4 Cs Diamond Grading

Cut

More than 100 million diamonds are sold in the United States each year, yet most consumers know very little about the product they are purchasing, and how that product is valued. The 4 Cs represent the four variables that are used to calculate the quality and value of a diamond. Both rough and cut diamonds are separated and graded based on these four characteristics.

As a consumer, your first step in shopping for a diamond should be to learn and understand the "4 Cs" diamond grading system. It is important to learn how to read and understand the details of a GIA (Gemological Institute of America), AGL, or AGS (American Gem Society) "Diamond Certificate" or Sarin "Diamond Grading Report" or GIA 'Diamond Dossier®.' You will also want to familiarize yourself with the Federal Trade Commission (FTC) guidelines on jeweler conduct and consumer awareness. This will help you immensely when you are comparison shopping for diamonds.

CUT

Diamond Cut Quality

When jewelers judge the quality of a diamond cut, or "make", they often rate "Cut" as the most important of the "4 Cs." The way a diamond is cut is primarily dependent upon the original shape of the rough stone, location of the inclusions and flaws to be eliminated, the preservation of the weight, and the popularity of certain shapes. Don't confuse a diamond's "cut" with it's "shape". Shape refers only to the outward appearance of the diamond (Fig. 5 below), and not how it is faceted.

The Importance of Cut Quality

When a diamond has a high quality cut (ideal cut), incident light will enter the stone through the table and crown, traveling toward the pavilion where it reflects from one side to the other before bouncing back out of the diamond's table toward the observer's eye (see Fig. 1 below). This phenomenon is referred to as "light return" (Fig. 2 below) which affects a diamond's brightness, brilliance, and dispersion. Any light-leakage caused by poor symmetry and/or cut proportions (off-make) will adversely affect the quality of light return.

The "Shallow Cut" and "Deep Cut" examples in Fig. 1 show how light that enters through the table of a Modern Round Brilliant diamond reaches the pavilion facets and then leaks out from the sides or bottom of the diamond rather than reflecting back to the eye through the table. Less light reflected back to the eye means less "Brilliance". In the "Ideal Cut" example, most of the light entering through the table is reflected back towards the observer from the pavilion facets.

Four Cs Diamond Cut Quality

Keep in mind that the variance in proportions between an "Ideal Cut" (ideal make) and a "Fair, Poor, Shallow or Deep Cut" may be difficult to discern to the novice observer, although there will be a lack of brilliance, scintillation, and fire. Cut quality is divided into several grades listed below.

* Ideal Cut
* Premium Cut
* Very Good / Fine Cut
* Good Cut
* Fair Cut
* Poor Cut

Cut Proportions

In the past, the "Cut" quality of the "4 Cs" was the most difficult part for a consumer to understand when selecting a good diamond because a GIA or AGS certificate did not show the important measurements influencing cut (i.e. pavilion and crown angle) and did not provide a subjective ranking of how good the cut was. Only a trained eye could see the quality of a good cut. All of that has changed with the AGS Cut Grading system and GIA's new "Cut Grading System".

GIA vs AGS Cut Grading

GIA's new cut-grading system is based on averages that are rounded-up to predict 'light performance,' while AGS uses a more exacting combination of proportional facet ratios along with ray-tracing metrics to calculate light return. The "Ideal" designation is an AGS term that is not found on an GIA report. The GIA will give a symmetry demerit for what it calls "non-standard brillianteering" which some manufacturers use to 'improve' on the standardized Tolkowsky-type cuts.

The proportion and symmetry of the cuts as well as the quality of the polish are factors in determining the overall quality of the cut. A poorly cut diamond with facets cut just a few degrees from the optimal ratio will result in a stone that lacks gemmy quality because the "brilliance" and "fire" of a diamond largely depends on the angle of the facets in relation to each other. An Ideal Cut or Premium Cut "Round Brilliant" diamond has the following basic proportions according to the AGS:

* Table Size: 53% to 60% of the diameter
* Depth: 58% to 63% of diameter
* Crown Angle: 34 to 35 degrees
* Girdle Thickness: medium to slightly thick
* Facets: 58 (57 if the culet is excluded)
* Polish & Symmetry: very good to excellent

The girdle on a Modern Round Brilliant can have 32, 64, 80, or 96 facets which are not counted in the total number of facets (58). The crown will have 33 facets, and the pavillion will have 25 facets. Other variations of the "Modern Round Brilliant" include the "Ideal Brilliant" which was invented by Johnson and Roesch in 1929, the "Parker Brilliant" invented in 1951, and the "Eulitz Brilliant" invented in 1972.

Poor Faceting and Symmetry

Due to the mathmatics involved in light refraction, a Round Brilliant cut that does not have the proper proportions and symmetry (off-make) will have noticeably less brilliance. Common cutting problems can occur during the faceting process, when one incorrect facet angle can throw off the symmetry of the entire stone. This can also result in the undesirable creation of extra facets beyond the required 58. The chart below shows several common problems to look for.

Poor Faceting and Symmetry

For a Modern Round Brilliant cut (Tolkowsky Brilliant), there is a balance between "brilliance" and "fire". A diamond cut for too much fire will look like cubic zirconia, which gives out much more fire than a real diamond. A well executed round brilliant cut should reflect the maximum amount light from the interior pavilion facets, out through the table, making the diamond appear white when viewed from the top. A cut with inferior proportions will produce a stone that appears dark at the center (due to light leaking out of the pavilion) and in some extreme cases the ring settings may show through the top of the diamond as shadows.

AGS Triple-0 Certification

The American Gem Society (AGS) is the industry leader in laboratory testing of round gems for cut grade and quality. In order for a diamond to receive a "Triple-0" grading, all three categories of cut (Polish, Symetry, Proportion) must meet the "ideal" criteria. A Triple-0 diamond can also be called a "Triple Ideal Cut" or "AGS-Ideal Zero" diamond.

Hearts and Arrows Diamonds

A perfectly proportioned ideal cut that is cut to the exacting specifications of a Tolkowsky Cut, Eppler Cut (European Standard), or a Scan D. N. Cut (Scandinavian Standard) will display a "Hearts and Arrows" pattern when observed through a IdealScope (arrows only), or a H & A Viewer gemscope (FireScope).

Diamond Cutting Background

One of the hardest substances on earth, only a diamond is hard enough to cut other diamonds. Polishing and mounting add brilliance to the stone and increase it's value. Diamond cutting can be traced back to the late Middle Ages. Prior to this time, diamonds were used in their natural octahedral state. The first improvements on nature's design involved a polishing of the crystal faces, which was called the "Point Cut". As further refinement progressed, one half of the crystal would be cut off, creating the "Table Cut". At the time, diamonds were valued primarily for their luster and hardness. Table Cut diamonds appeared black to the eye. The Modern Round Brilliant cut (below) is the culmination of several hundred years of experimentation and development.

Cutting a Rough Diamond

Cutting a raw diamond into a faceted and polished gem-quality stone is a multi-step process. Each step is critical to the final outcome. The steps are:

* Marking
* Cleaving
* Sawing
* Bruting (Girdling)
* Faceting

Marking: A rough stone is marked prior to cleaving or sawing to determine the direction of the grain or "cleavage", eliminate waste, and bypass inclusions or imperfections. The natural shape of the rough stone will also be a major factor in deciding how to cut the stone. An octahedron can be cut into one or two Round Brilliants but a square Princess cut will result in the least amount of waste due to the square shape of the stone. Asymmetrical crystals such as macles are used primarily for fancy cuts. Cubic shapes are ideal for a square Princess or Radiant cut. High-tech computerized helium and oxygen analyzers are now used to evaluate a stone prior to cutting.

Rough Diamond Shapes

Cleaving: Cleaving refers to splitting a stone along its grain by striking it. A rough stone is cleaved if there are conspicuous defects and/or inclusions which would prevent it from being made into a single gemstone. Cleavage is the tendency of crystalline materials to split along definite planes. Due to its atomic structure, a diamond can be cleaved in four directions parallel to each of the four octahedron crystal faces. Cleaving is a critical step as a mistake by the "cleaver" could shatter the stone.

Sawing: A stone-cutting saw is a thin disk made of phosphor bronze. As the saw blade rotates it continues to pickup or "recharge" itself with diamond dust which is the cutting agent. It can take several hours for the saw blade to cut through a 1k rough diamond.

Bruting: The rough is placed in a chuck on a lathe. While the rough stone rotates on the diamond lathe, a second diamond mounted on a dop is pressed against it, rounding the rough diamond into a conical shape. This step is also referred to as rounding or bruting.

Faceting: To facet a "Round Brilliant", a "blocker" or "lapper" will cut the first 18 main facets, then a "brillianteer" will cut and polish the remaining 40 facets. The cutting (placing) and polishing of each facet is accomplished by attaching the stone to a dop stick and pressing it against a revolving cast iron disk, scaife, or lap on a Facetron that has been charged with diamond dust. During this faceting stage the angles of each facet must be cut to an exacting standard in order to yield maximum brilliancy and maintain symmetry.

Diamonds Ideal Cut - Modern Round Brilliant Diamond

Ideal Cut vs Standard Cut Diamond

When deciding how to cut a rough diamond, a cutter must make a cost-benefit analysis as to how to maximize the cut stone's value. As stated in the previous section, an octehedral rough will yield two round brilliant cut stones. On the one hand, the objective is to maximize carat weight, but in order to do this, compromises would have to be made. If the stone has a colorless D through F rating and has very few inclusions, it would be cost effective to sacrifice some carat weight in order to finish with two "Ideal" cuts. If, on the other hand, the rough stone has some coloration and/or is heavily included, it may be better to aim for a higher carat weight with a "Standard" cut.

Ideal vs Standard Cut

Parameters Ideal Cut Standard (Premium) Cut

Rough Material Loss Greater Loss Higher Yield
Finished Stones Lower Carat Weight Higher Carat Weight
Cutting Time 2 to 4 Days 1 to 2 Days
Crown Symmetry Ideal Shallow Crown
Pavilion Symmetry Ideal Deep Pavilion
Girdle Symmetry Ideal Thick Girdle

The Modern Round Brilliant Cut

The modern "Round Brilliant Cut" (below) was developed by Belgian diamond-cutter Marcel Tolkowsky in 1919. This cut is also known as the "Tolkowsky Cut" and "Tolkowsky Brilliant." Even with modern techniques, the cutting and polishing of a diamonds resulted in a loss of as much as 50% of the stone's total weight. The round brilliant cut was a partial solution to this problem. The round brilliant cut is beneficial when the crystal is an octahedron, as two stones could be cut from one crystal.

In the diagram of a "Round Cut" diamond (above and below), you will see that there are 8 "star" facets, 8 "kite" facets, 16 "upper girdle" facets, 16 "lower girdle" facets, 8 "pavilion" facets, 1 "culet" facet on the bottom, and one "table" facet on the top of the stone for a total of 58 facets.

An "Ideal Cut", "Premium Cut" or "Modern Round Brilliant" (Tolkowsky Round Brilliant) diamond as shown in the diagrams above would have the following basic proportions according to the AGS:

* Table Size: 53% to 57% of the diameter
* Total Depth: 58% to 63% of diameter
* Crown Angle: 34 to 35.5 degrees
* Pavillion Depth: 42.5% to 43.5%
* Girdle Thickness: medium to slightly thick
* Culet: pointed, very small to small

In the 1970s, Bruce Harding developed new mathematical models for gem design. Since then, several groups have used computer models and specialized scopes to design new diamond cuts.

Tolkowsky, Eppler & Scan D.N.

Variations on the Tolkowsky Brilliant (Fig 3 below) are the "Eppler" (European Practical Fine Cut, or Feinschliff der Praxis) with a table width of 56%, crown height of 14.4%, and overall height of 57.7%. The "Scan D.N." (Scandinavian standard, or Scandinavian Diamond Nomenclature) diamond cut has a table width of 57.5%, crown height of 14.6% and overall height of 57.7%. Other variations of the MRB include the "Ideal Brilliant", invented in 1929, the "Parker Brilliant" invented in 1951, and the "Eulitz Brilliant" invented in 1972.

To quantify a diamond's cut quality, gem labs will use a variety of equipment such as a BrilliantScope, H&A Viewer, Ideal Scope, Sarin Diamension and/or FireTrace.

AGS Triple Ideal or 'Triple 0' Grade

The AGSL grades a diamond's cut quality using three parameters: Polish, Symmetry, and Proportions. Each parameter is given a 'grade' from 0 (Ideal) to 10 (Poor). When all three parameters are in perfect harmony the diamond is given a "Triple 0" or "Triple Ideal" grading. The AGSL grades a diamond's symmetry and proportions according to where facets intersect, and crown/pavilion angles, but does not measure or quantify relative facet angles and/or individual facet ratios. A perfect blending of facet symmetry, facet ratios, and facet angles will yield a perfect 'Hearts & Arrows' Diamond pattern when viewed through a H&A Viewer.

Diamonds Structural Properties & Chemistry

Structural Properties

Formation

Diamonds are formed when carbon deposits are exposed to high pressure and temperature for prolonged periods. Deep within the earth, there are regions that are at a high enough temperature (900ºC to 1400ºC) and pressure (5 to 6 GPa) that the formation of diamonds is thermodynamically possible. Under the continental crust, diamonds form starting at depths of about 90 miles (150 kilometers), where pressure is roughly 5 gigapascals and the temperature is around 2,200 degrees Fahrenheit (1,200 degrees Celsius). Diamond formation under oceanic crust takes place at greater depths due to lower surface temperatures. This requires a higher pressure for diamond formation. Long periods of exposure to these high pressures and temperatures allow diamond crystals to grow larger.

Diamonds are mined in alluvial mining operations when they are not located along a "kimberlite pipe". Kimberlite is an ultrapotassic, ultramafic, igneous rock composed of garnet, olivine, phlogopite, and pyroxene with a variety of other trace minerals. Kimberlite occurs in the Earth's crust in vertical structures known as kimberlite pipes.

Basic Properties

A diamond it is the hardest naturally occurring material with a relative hardness of 10 on the Mohs scale. Diamond is one of several allotropes of carbon, the principle allotrope being graphite. Allotrope" or "Allotropy" specifically refers to the chemical bond structure between atoms. A diamond is a transparent, optically isotropic crystal with a high dispersion of 0.044, a refractive index of 2.42, and a specific gravity of 3.52.

Crystal Structure & Hardness

The chemical bond structure of diamond crystal is what gives this gemstone its hardness, toughness, and differentiates it from graphite. The name "diamond" (also known as adamant), is derived from the Greek adamas, "untameable", "invincible" or "unconquerable," referring to its incredible hardness (10 on the Mohs scale of mineral hardness). A Type 2-A diamond has a hardness value of 167 GPa (±6) when scratched with an ultrahard fullerite tip, and a hardness value of 231 GPa (±5) when scratched with a diamond tip. The material "boron nitride", when in a form structurally identical to diamond, is nearly as hard as diamond. Additionally, a currently hypothetical material, beta carbon nitride, may also be as hard or harder.

Crystal Habit

Diamonds have a characteristic crystalline structure. This means that crystals usually "grow" in an orderly and symmetrical arrangement. The natural form, or habit, of a diamond is octahedral (above). In nature perfect crystals are rare. The external shape of the crystal does not always reflect the internal arrangement of atoms. When stones have irregular external shapes or arrangements of crystal faces, they are termed "subhedral" or "anhedral." Trace impurities, crystal twinning, and growth conditions (heat, pressure and space) can also effect the final shape of a formed crystal.

Toughness

In the field materials science and metallurgy, toughness is the resistance to fracture of a material when stressed or impacted. Toughness is measured in units of "joules" per cubic meter (J/m3) in the SI system and "pound-force" per square inch in US units. Unlike hardness, which only denotes resistance to scratching, diamond's toughness is only fair to good. Particular cuts of diamonds are more prone to breakage, and thus may be uninsurable by reputable insurance companies. The culet is a facet designed exclusively to resist breakage. By contrast, very thin girdles are prone to much higher breakage.

Although diamond is the "hardest" (most scratch resistant) mineral, with a Mohs rating of 10, its toughness rating is only good. Sapphire has a hardness rating of 9, meaning that a diamond is 4 times "harder" than sapphire, yet sapphire has a toughness rating of excellent. Hematite has a hardness of only 5.5 to 6.5 but its toughness rating is also excellent.

Optical Properties

Fluorescence

The luster (or "lustre") of a diamond is described as adamantine, which means diamond-like. The word luster traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance. Some diamonds exhibit fluorescence of various colors under long wave ultra-violet light, but generally bluish-white, yellowish or greenish fluorescence under X-rays. Fluorescence is an optical phenomenon in which a molecule absorbs a high-energy photon, and re-emits it as a lower-energy (or longer-wavelength) photon. Some diamonds, particularly Canadian diamonds, show no fluorescence. Diamonds have an absorption spectrum consisting of a fine line in the violet at 415.5 nm. Colored stones show additional bands. Brown diamonds show a band in green at 504 nm, sometimes accompanied by two additional weak bands also in green.

Type I & Type II Diamonds

Up to 99% of all natural diamonds are classified as Type I and contain nitrogen atoms as an impurity, replacing carbon atoms within the lattice structure. Nitrogen impurities in Type I diamonds are evenly dispersed throughout the stone, absorbing some of the blue spectrum, thereby making the diamond appear yellow. There are two subcategories (a and b) within each diamond 'type' that are based on a stone's electrical conductivity.

Diamonds that have formed under extremely high pressure for longer periods have a lower nitrogen content, permitting the passage of blue light and making the stone have a 'colorless' (D) appearance. Type II diamonds do not contain detectable nitrogen, thereby allowing the passage of short-wave ultra-violet (SWUV) light through the stone. Natural blue Type II diamonds containing boron impurities and are good conductors of electricity and are classified as Type IIb diamonds, and diamonds that lack boron impurities are classified as Type IIa. Type IIa diamonds have a near-perfect crystal structure making them highly transparent and colorless, with high thermal conductivity. Type IIa diamonds are very rare and some of the finest historical stones such as the Cullinan and Koh-i-Noor are both Type IIa diamonds.

Refraction & Coloration

Diamond is singly refractive with a refractive index of 2.417. Diamonds exhibit Pseudochromatic Coloration giving the appearance of "color" that is not caused by any actual color in the mineral, but from varying optics effects created by spectral dispersion (Fire) and refraction.

Diamond Chemistry - Optical Properties

Diamonds can also exhibit Allochromatic Coloration that is caused by chromophores from the nitrogen trace impurities found within crystalline structure. It is Nitrogen that produces the yellow color in diamond.

Color & Composition

Diamonds occur in a wide variety of colors: colorless, white, blue, steel (grey), yellow, orange, pink, red, brown, green, and black. Colored diamonds contain certain impurities or structural defects that cause the coloration, while "pure" diamonds are transparent and colorless.

Type 1 diamonds have nitrogen atoms as the main impurity. If they are in clusters they do not affect the diamond's color (Type 1-A). If dispersed throughout the crystal they give the stone a yellow tint (Type 1-B). Typically a natural diamond crystal contains both Type 1-A and Type 1-B material. Synthetic Diamonds containing nitrogen are Type 1-B.

Type 2 diamonds have very few nitrogen impurities. Type IIa diamond can be colored pink, red, or brown due to structural anomalies arising through plastic deformation. Type 2-B is the blue diamond containing scattered boron within the crystal matrix.

Experimentation in the late 18th century showed that diamonds were made of carbon. By igniting a diamond in an oxygen atmosphere, the end product of the combustion was carbonic acid gas (or carbon dioxide). Diamond had previously been shown to burn in experiments conducted in the ancient Roman period although the reason was not understood at the time. Diamonds are carbon crystals that form deep within the Earth under high temperatures and extreme pressures. At surface air pressure (one atmosphere), diamonds are not as stable as graphite, and so the decay of diamond is thermodynamically favorable.

Electromagnetic Properties

Insulators or Semiconductors

Diamond is a good electrical insulator, with the exception of most natural blue diamonds, which are actually semiconductors. Natural blue diamonds have been found to owe their color to an overabundance of hydrogen atoms. Most natural blue diamonds are not semiconductors. Natural blue diamonds containing boron and synthetic diamonds doped with boron are p-type semiconductors. If an n-type semiconductor can be synthesized, electronic circuits could be manufactured out of diamonds. In October of 2004 superconductivity was found to occur in heavily boron-doped microwave plasma-assisted chemical vapor deposition (MPCVD) diamond below the superconducting transition temperature of 7.4K.

Thermal Properties

Diamonds are a good conductor of heat, unlike most electrical insulators. Most natural blue diamonds contain boron atoms which replace carbon atoms in the crystal matrix, and also have high thermal conductance. Purified synthetic diamond has the highest thermal conductivity (2000-2500 W/(m-K, five times greater than pure copper) of any known solid at room temperature. Because of a diamond's high thermal conductance, it is used in semiconductor manufacture to prevent silicon and other semiconducting materials from overheating.

Improvements To Nature

Enhanced Diamonds

"Diamond Enhancements" are specific treatments, performed on cut and polished natural diamonds, which are designed to "improve" the gemological characteristics of the stone. These treatments include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond. A trained gemologist will be able to identify any "enhancements" to the stone.

Synthetic Diamonds & Diamond Simulants

Synthetic Diamonds

First conceived of by French chemist Henri Moissan in 1892, tiny fragments of synthetic diamond were created by heating charcoal (carbon) to very high temperatures (4000º C) in a molten iron crucible, using an electric furnace constructed with blocks of lime. Once the furnace had rendered the whole mass into a liquid, the crucible and its contents were rapidly cooled by immersing them in cold water. The sudden cooling and shrinkage of the molten iron crucible created enough pressure to crystallize the molten carbon into tiny diamond fragments.

The first practical application of Moissan's concept was the 'belt press' HTHP (high-temperature, high-pressure) process for synthesizing industrial diamonds, developed by H.Tracy Hall for the General Electric Company in 1954. This process has been steadily improved upon throughout the last 50 years.

Although synthetic diamonds (aka lab diamonds, cultured diamonds) are a laboratory-grown simulation of the natural stone, they have the identical carbon-based chemical properties of natural diamond. Synthetic diamonds are increasingly used in the jewelry trade under the "Apollo Diamond," "Chatham Created Gems," "Gemesis" or "Tairus" trade names.

High-Temperature High-Pressure (HTHP)

One of the methods used to create laboratory-grown synthetic diamonds is the High-Temperature High-Pressure (HTHP) technique (GE POL), using a four-anvil 'tetrahedral press,' or six-anvil 'cubic press.' A diamond seed is placed into a growth camber and a combination of heat and pressure are applied to the 'seed' in a process that attempts to replicate the natural conditions for diamond-formation. The HTHP growth process can take 7 to 10 days to complete. Synthetic diamonds can also be treated with HTHP to alter the optical properties of the stones, making them difficult to differentiate from a natural diamonds.

Chemical Vapor Deposition (CVD)

The 'Chemical Vapor Deposition' method was developed in the 1980s and uses a lower pressure growth-environment than HTHP. A seed or 'substrate' is placed in the growth camber and a combination of heat and pressure are applied while a vaporized carbon plasma, combined with hydrogen is applied (deposited) to the substrate in layers. The vaporized carbon gases are energized using microwave energy, and the entire growth process takes several days to complete.

A 'cultured' or 'lab grown' diamond will have the same cleavage, hardness, light dispersion, refractive index, specific gravity, and surface luster as a natural diamond. Synthetic diamonds can contain some inclusions, ranging in clarity from IF to SI or I, and may have a slightly yellowish hue (not colorless) due to nitrogen impurities that are dispersed through out the crystal lattice structure, thereby absorbing the blue end of the light spectrum. Synthetics can be detected using infrared, ultraviolet, or X-ray spectroscopy, or by measuring UV fluorescence with a DiamondView tester.

Synthetic Diamond Manufacturers

Apollo Diamonds

Apollo Diamond, inc. in Boston, Massachusetts grows colorless (D to M) and some fancy colored diamonds using a proprietary variation of the Chemical Vapor Deposition (CVD) technique. Apollo Diamonds are cut in sizes from .25 carats to 1 carat, and clarity grades are from IF to SI. Their cut stones are available in round brilliant, emerald, princess, and rose cuts. Each cut stone is laser inscribed with the company name and serial number.

Chatham Created Diamonds

Chatham is a San Francisco based company that grows only fancy-colored diamonds in colors ranging from champagne and canary yellow to pink and midnight blue. Pricing ranges from $6,500 to $9,500 per carat and each stone is laser inscribed with the company name and serial number.

Gemesis Cultured Diamonds

Gemesis only grows fancy colored diamonds and to insure easy identification as a man-made product, each cut stone over .25 carats is laser inscribed with the company name and serial number. Gemesis is located in Sarasota, Florida.

Tairus Created Gems

Tairus Created Gems is a Russian company that grows fancy colored diamonds in a "Split Sphere" system, crystalizing the carbon in an alkaline carbonate-fluid solution that is similar to diamond-bearing metamorphic rock. Rough sizes from .30 carats to 3 carats, and stones are cut to order. Tairus Created Gems are sold exclusively through Tairus Thailand Co., Ltd. of Bangkok Thailand.

Diamond Simulants

Diamond "simulants" (simulated diamonds or fake diamonds) are man-made gemstones that look like (or simulate) the appearance of natural diamonds, but are not a carbon compound with a diamond crystalline structure. Common simulants include:

* Cubic Zirconia (CZ) (1976-) Czarite, Diamonite, Diamond Essence, Phianite
* Gadolinium Gallium Garnet (GGG) (1972-1975)
* Moissanite (1998 - )
* Strontium Titanate (ST) (1955 - 1970) Diagem, Fabulite
* Synthetic Rutile (1946-1955) Diamothyst, Java Gem, Rainbow Diamond, Rutania, Titangem
* Synthetic Sapphire (1900-1947) Diamondette, Diamondite, Jourado Diamond, Thrilliant
* Synthetic Spinel (1920-1947) Corundolite, Lustergem, Magalux, Radient
* Yttrium Aluminum Garnet (YAG) (1970-1975) Diamone, Diamonaire, Diamonte, Geminaire

In the early 1900's, colorless synthetic sapphire (aka Diamondite) was a popular diamond simulant. produced using the Verneuil (flame-fusion) Process. In the late 1940's Diamondite gave way to Synthetic Rutile which was popular until the advent of YAG in the early 1970's. With the advent of Cubic Zirconia in the mid 1970's, and Moissanite in 1998, most of these lesser simulants fell by the wayside.

Fancy Colored Diamonds | Pink, Yellow & Cognac Diamonds

Fancy Colored Diamond

Diamonds can occur in all colors of the spectrum, and their color is due to trace impurities of nitrogen and/or hydrogen (yellow, brown diamonds), boron (blue diamonds), radiation exposure (green diamonds) or irregular growth patterns within the crystal (pink, red diamonds).

Colorless diamonds would normally be priced much higher than yellow diamonds. However, when a diamond's color is more intense than the "Z" grading, it enters the realm of a "Fancy Color" diamond. In this case, the intensity of the color in the diamond can plays a significant role in its value. The value of a Fancy Color Diamond can surpass that of colorless diamonds if the intensity of the color is high and the color is rare.

Diamond Hues

A fancy brown (or Fancy Cognac), green, or yellow diamond may have a relatively low value when compared to a colorless diamond. However, certain fancy-colored diamonds such as pink (Condé), blue (Hope Diamond), green (Ocean Dream), and red (Hancock Diamond) are particularly valuable. Once thought to be of little value, fancy pink diamonds can command very high prices as they have become increasingly popular.

Fancy Diamond Color

Brown diamonds, which are generally less appreciated than other fancy colors and therefor, sold at a greater discount, have become more commonplace as Australian colored diamonds have gained in popularity.

Fancy Yellow Diamonds (Canary Yellow)

Fancy yellow diamonds owe their color the presence of nitrogen impurities which absorb the blue end of the color spectrum. The GIA grades fancy diamond color by quantifying the saturation, hue, and value (darkness) using nine classifications ranging from 'Faint' to 'Vivid.'

GIA Fancy Diamond Color Grading

GIA 'Fancy Yellow' Diamond Color Saturation Designations

* Faint - M
* Very Light - N to R
* Light - S to Z
* Fancy Light - Start of 'Fancy'
* Fancy
* Fancy Dark
* Fancy Intense
* Fancy Deep
* Fancy Vivid - Highest Saturation

One of the largest, and most valuable Fancy Yellow diamonds in the world is the 'Tiffany Diamond,' found in Kimberly, South Africa in 1878. The rough stone weighed 287.42 carats, and was cut into a 128.54 carat cushion cut with an estimated value in the millions of dollars.

Pink Diamonds

The pink color within these rare diamonds is due to irregular crystal growth patterns, causing microscopic imperfections within the lattice structure. One of the world's only major sources for rare pink diamonds is the Argyle Mine in Australia. Pink diamonds are similar to pink sapphire in color, yet considerably more expensive. 1PP is the highest quality designation for Pink Diamond, having a pure magenta color with deep saturation. As the numbers go lower (8PP) the color is paler. An 1P designation would have less blue and more brownish-red. Only 1% to 2% of the diamonds produced at the Argyle Mine are high-quality pink specimens.

Fancy Pink/Brown Diamond Color (Hue) Designations

* 1PP to 8PP - Pink (Magenta-pink) 1 is darkest
* 1P to 8P - Pink (Reddish-pink) 1 is darkest
* 1BP to 8BP - Pink (Brownish-pink) 1 is darkest
* PC3 to PC1 - Champagne 3 is darkest
* C8 to C1 - Cognac 8 is darkest

Chameleon Diamonds

There is a very rare olive-grayish color-changing diamond called "Chameleon Diamond" (below, left), which changes hue from grayish-blue or olive-green to yellowish-green or straw-yellow under different lighting conditions (darkness, bright light), lighting color temperatures (incandescent, halogen, daylight) and ambient temperature changes. This Chameleon-like phenomenon was first documented by the GIA in the early 1940s.

Chameleon Diamonds & Pink Diamond Grading

Chameleon diamonds can be forced to temporarily change to a yellowish-green color by exposing them to heat (150º C to 250º C), or short-term storage (up to 24 hours) in total darkness [9]. Exposure to direct sunlight will bring out an olive-green color. The color change effect is temporary, and will totally reverse itself when conditions re-stabilize. It is believed that the color changing effect is due to a higher than normal amount of hydrogen impurities.

Green Diamonds

Green diamonds owe their hue to millions of years of exposure to naturally occurring gamma and/or neutron radiation, and are typically found in alluvial secondary deposits. Primary sources are in south-central Africa. Most 'green' diamonds are actually a yellowish-green, greyish-green, or a combination of the two. Intense, pure green hues, as in the one-of-a-kind 5.51 carat blue-green 'Ocean Green Diamond' or the 41 carat apple-colored 'Dresden Green Diamond' are virtually non-existant. Green diamonds can range from $35,000 to $500,000 per carat. Irradiation can artificially induce a green color in diamonds.

The Elusive Red Diamond

Perhaps the rarest diamond color of all is the elusive Red Diamond. There are fewer than twenty known specimens of "natural" red diamond. The first red diamond to be found was the 1 carat 'Halphen Red,' discovered during the 18th century.

The most famous red diamond (the Hancock Red) was found in Brazil, and weighed a modest 0.95-carats. It was cut into a round brilliant named after its owner, Warren Hancock. The Hancock Red sold at Christie's auction house for a staggering $926,000 in 1987. Other famous reds are the Moussaieff Diamond weighing 13.90 carats, and the De Young Red weighing 5.03 carats. Pricing in today's market is in the range of $1 million dollars per carat.

Fashion Trends

While prices will undoubtedly remain predictably higher for colorless diamonds and certain rare fancy-colored diamonds, the specific color most valued by a given consumer is largely influenced by current styling trends and personal taste. On thing is certain, as the tastes and preferences of the consumer shift in priorities, so will the market prices of sought-after commodities that are in limited supply.

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