Due to its low cost and close visual likeness to diamond, cubic zirconia has remained the most gemologically and economically important diamond simulant since 1976.

The high price of gem-grade diamonds has created a large demand for materials with similar gemological characteristics, known as diamond simulants or imitations. Simulants are distinct from synthetic diamond, which unlike simulants is actual diamond, and therefore has the same material properties as natural diamond. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection. Photo of a round brilliant-cut cubic zirconia by Gregory Phillips. ... A round brilliant-cut cubic zirconia Cubic zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... This article is about the gemstone. ... Gemology (gemmology outside the United States) is the science, art and profession of identifying and evaluating gemstones. ... A colourless synthetic diamond produced via chemical vapour deposition Synthetic diamond is a diamond produced through chemical or physical processes in a factory. ... This article addresses the material properties of diamond. ... This article addresses treatments designed to enhance the gemological characteristics of diamond. ... Dispersion of a light beam in a prism. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ...

The most common diamond simulants are high-leaded glass (i.e., rhinestones) and cubic zirconia (CZ), both artificial materials. A number of other artificial materials, such as strontium titanate and synthetic rutile have been developed since the mid 1950s, but these are no longer in common use. Introduced at the end of the 20th century, the artificial product moissanite has gained popularity as a supposedly superior diamond simulant, although its much higher cost and limited production have kept it a relatively minor simulant in the jewelry marketplace. The term leaded glass either refers to: glass containing lead oxide, which increases its density and enhances its refraction and dispersion of light. ... A rhinestone or paste is a diamond simulant made from rock crystal, glass or acrylic. ... A round brilliant-cut cubic zirconia Cubic zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ... Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. ... Rutile in trellis texture characteristic of secondary rutile. ... // Recovering from World War I and its aftermath, the economic miracle emerged in West Germany and Italy. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. ...

Desired and differential properties

See also: Material properties of diamond

In order to be considered for use as a diamond simulant, a material must possess certain diamond-like properties. The most advanced artificial simulants have properties which closely approach diamond, but all simulants have one or more features that clearly and (for those familiar with diamond) easily differentiate them from diamond. To a gemologist, the most important of differential properties are those that foster non-destructive testing, and most of these are visual in nature. Non-destructive testing is preferred because most suspected diamonds are already cut into gemstones and set in jewelry, and if a destructive test (which mostly relies on the relative fragility and softness of non-diamonds) fails it may damage the simulant—this is not an acceptable outcome for most jewelry owners, as even if a stone is not a diamond it may still be of value. This article addresses the material properties of diamond. ... Gemology (gemmology outside the United States) is the science, art and profession of identifying and evaluating gemstones. ... Jewelry (the American spelling; spelled jewellery in Commonwealth English) consists of ornamental devices worn by persons, typically made with gems and precious metals. ...

Following are some of the properties by which diamond and its simulants can be compared and contrasted.

Durability and density

The Mohs scale of mineral hardness is a non-linear scale of common minerals' resistances to scratching. Diamond is at the top of this scale (hardness 10) as it is the hardest naturally occurring material known (the hardest substance known today is the man-made substance aggregated diamond nanorods). Since diamonds are unlikely to encounter substances that can scratch it, other than another diamond, diamond gemstones are typically free of scratches. Diamond's hardness also is visually evident (under the microscope or loupe) by its highly lustrous facets (described as adamantine) which are perfectly flat, and its crisp, sharp facet edges. For a diamond simulant to be effective, it must be very hard relative to most gems. Most simulants fall far short of diamond's hardness, so they can be separated from diamond by their external flaws and poor polish. The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. ... Minerals are natural compounds formed through geological processes. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... Aggregated diamond nanorods, or ADNRs, are an allotrope of carbon believed to be the least compressible material known to humankind, as measured by its isothermal bulk modulus; aggregated diamond nanorods have a modulus of 491 gigapascals (GPa), while a conventional diamond has a modulus of 442 GPa. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ... A magnifying glass A magnifying glass is a single convex lens which is used to produce a magnified image of an object. ... For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... Facets are flat faces on geometric shapes. ...

In the recent past, the so-called "window pane test" was commonly thought to be an assured method of identifying diamond. It is a potentially destructive test wherein a suspect diamond gemstone is scraped against a pane of glass, with a positive result being a scratch on the glass and none on the gemstone. The use of hardness points and scratch plates made of corundum (hardness 9) are also used in place of glass. Hardness tests are inadvisable for three reasons: glass is fairly soft (typically 6 or below) and can be scratched by a large number of materials (including many simulants); diamond has four directions of perfect and easy cleavage (planes of structural weakness along which the diamond could split) which could be triggered by the testing process; and many diamond-like gemstones (including older simulants) are valuable in their own right. A pickguard (also known as scratchplate and uncommonly, a finger rest) is a piece of plastic or other laminated material that is placed under the strings on the body of a guitar, mandolin or similar plucked string instrument. ... Corundum (from Tamil kurundam) is a crystalline form of aluminium oxide and one of the rock-forming minerals. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ...

The specific gravity (SG) or density of a gem diamond is fairly constant at 3.52. Most simulants are far above or slightly below this value, which can make them easy to identify if unset. High-density liquids such as di-iodomethane can be used for this purpose, but they are all highly toxic so are usually avoided. A more practical method is to compare the expected size and weight of a suspect diamond to its measured parameters: for example, a cubic zirconia (SG 5.6–6) will be 1.7 times the expected weight of an equivalently sized diamond. Relative density (also known as specific gravity) is a measure of the density of a material. ... The venom of the black widow spider is a potent latrotoxin. ... A round brilliant-cut cubic zirconia Cubic zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ...

Optics and color

Diamonds are usually cut into brilliants to bring out their brilliance, the amount of light reflected back to the viewer, and fire, the degree of colorful prismatic flashes seen. Both properties are strongly affected by the cut of the stone, but they are a function of diamond's high refractive index (RI; the degree to which incident light is bent upon entering the stone) of 2.417 (as measured by sodium light, 589.3 nm) and high dispersion (the degree to which white light is split into its spectral colors within the stone) of 0.044, as measured by the sodium B and G line interval. Thus, if a diamond simulant's RI and dispersion are too low it will appear comparatively dull or "lifeless"; if the RI and dispersion are too high, the effect will be considered unreal or even tacky. Very few simulants have closely approximating RI and dispersion, but even the close simulants can be separated by an experienced observer. Direct measurements of RI and dispersion are impractical (a standard gemological refractometer has an upper limit of about RI 1.81), but several companies have devised reflectivity meters to gauge a material's RI indirectly by measuring how well it reflects an infrared beam. A scattering of brilliant cut diamonds shows off the many reflecting facets. ... If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... A sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. ... Dispersion of a light beam in a prism. ... A spectral color is a color that is part of the optical spectrum. ... A refractometer is an optical instrument that is used to determine the refractive index of a substance or some physical property of a substance that is directly related to its refractive index. ... In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; , the intrinsic reflectance of the surface, irrespective of other parameters such as the... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...

Perhaps equally as important is optic character. Diamond and other cubic (and also amorphous) materials are isotropic, meaning light entering a stone behaves the same way regardless of direction. Conversely, most minerals are anisotropic which produces birefringence or double refraction of light entering the material in all directions other than an optic axis (a direction of single refraction in a doubly refractive material). Under low magnification, this birefringence is usually detectable as a visual doubling of a cut gemstone's rear facets or internal flaws. An effective diamond simulant should therefore be isotropic. In crystallography, the cubic crystal system (or isometric crystal system) is the most symmetric of the 7 crystal systems. ... An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... The term optical axis has the following meanings: 1. ...

Under longwave (365 nm) ultraviolet light, diamond may fluoresce a blue, yellow, green, mauve, or red of varying intensity. The most common fluorescence is blue, and such stones may also phosphoresce yellow—this is thought to be a unique combination among gemstones. There is usually little if any response to shortwave ultraviolet, in contrast to many diamond simulants. Similarly, because most diamond simulants are artificial they tend to have uniform properties: in a multi-stone diamond ring, one would expect the individual diamonds to fluoresce differently (in different colors and intensities, with some likely to be inert). If all the stones fluoresce in an identical manner, they are unlikely to be diamond. UV redirects here. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Phosphorescent powder under visible light, ultraviolet light, and total darkness. ...

Most "colorless" diamonds are actually tinted yellow or brown to some degree, whereas artificial simulants are usually completely colorless—the equivalent of a perfect "D" in diamond color terminology. This "too good to be true" factor is important to consider; colored diamond simulants meant to imitate fancy diamonds are more difficult to spot in this regard, but the simulants' colors rarely approximate. In most diamonds (even colorless ones) a characteristic absorption spectrum can be seen (via a direct-vision spectroscope), consisting of a fine line at 415 nm. The dopants used to impart color in artificial simulants may be detectable as a complex rare earth absorption spectrum, which is never seen in diamond. Jewelers set diamonds in groups of similar colors. ... A materials absorption spectrum shows the fraction of incident electromagnetic radiation absorbed by the material over a range of frequencies. ... A spectroscope is a device which measures the spectrum of light. ... A dopant, also called doping agent and dope, is an impurity element added to a semiconductor lattice in low concentrations in order to alter the optical/electrical properties of the semiconductor. ... A rare earth is an oxide of a rare earth element. ...

Also present in most diamonds are certain internal and external flaws or inclusions, the most common of which are fractures and solid foreign crystals. Artificial simulants are usually internally flawless, and any flaws that are present are characteristic of the manufacturing process. The inclusions seen in natural simulants will often be unlike those ever seen in diamond, most notably liquid "feather" inclusions. The diamond cutting process will often leave portions of the original crystal's surface intact. These are termed naturals and are usually on the girdle of the stone; they take the form of triangular, rectangular, or square pits (etch marks) and are seen only in diamond. A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... Diamond Cutting is the art, skill and, increasingly, science of changing a diamond from a rough stone into an attractive gem. ...

Thermal and electrical

Diamond is an extremely effective thermal conductor and usually an electrical insulator. The former property is widely exploited in the use of an electronic thermal probe to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. As most simulants are thermal insulators, the thermistor's heat will not be conducted. This test takes about 2–3 seconds. The only possible exception is moissanite, which has a thermal conductivity similar to diamond: older probes can be fooled by moissanite, but newer testers are sophisticated enough to differentiate the two materials. In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... Lightning strikes during a night-time thunderstorm. ... This article or section is in need of attention from an expert on the subject. ... NTC thermistor, bead type, insulated wires Thermistor symbol A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ... In physics, heat, symbolized by Q, is defined as transfer of thermal energy [1] Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. ... Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. ...

A diamond's electrical conductance is only relevant to blue or gray-blue stones, because the interstitial boron responsible for their color also makes them semiconductors. Thus a suspected blue diamond can be affirmed if it completes an electric circuit successfully. General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ... An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ...

Artificial simulants

Diamond has been imitated by artificial materials for hundreds of years: advances in technology have seen the development of increasingly better simulants with properties ever nearer those of diamond. Although most of these simulants were characteristic of a certain time period, their large production volumes ensured that all continue to be encountered with varying frequency in jewelry of the present. Nearly all were first conceived for intended use in high technology, such as lasing mediums, varistors, and bubble memory. Due to their limited present supply, collectors may pay a premium for the older types. High tech refers to high technology, technology that is at the cutting-edge and the most advanced currently available. ... A laser system generally consists of three important parts: An energy source (usually referred to as the pump or pump source); A gain medium or laser medium; A mirror, or system of mirrors, forming an optical resonator. ... A varistor is an electronic component with a significant non-ohmic current-voltage characteristic. ... Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles, which each store one bit of data. ...

Summary table

The "refractive index(es)" column shows one refractive index for singly refractive substances, and a range for doubly refractive substances. The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... Dispersion of a light beam in a prism. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... This article is about the gemstone. ... Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... For Pb as an abbreviation, see Pb. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number thallium, Tl, 81 Chemical series poor metals Group, Period, Block 13, 6, p Appearance silvery white Atomic mass 204. ... Sapphire (from Hebrew: ספּיר Sapir) is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ... The spinels are any of a class of minerals which crystallize in the isometric system with an octahedral habit. ... Rutile in trellis texture characteristic of secondary rutile. ... Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. ... YAG Yttrium Aluminum Garnet Color: Wide range of colors Moh’s hardness: 8. ... Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. ... A round brilliant-cut cubic zirconia Cubic zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ... Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. ...

1700 onwards

The formulation of glasses using lead, alumina, and thallium to increase RI and dispersion began in the late Baroque period. These glasses are fashioned into brilliants, and when freshly cut they can be surprisingly effective diamond simulants. Known as rhinestones, pastes, or strass, glass simulants are a common feature of antique jewelry, and in such cases rhinestones can be valuable historical artifacts in their own right. The great softness (below hardnes 6) imparted by the lead means a rhinestone's facet edges and faces will quickly become rounded and scratched. Together with conchoidal fractures, and air bubbles or flow lines within the stone, these features make glass imitations easy to spot under only moderate magnification. In contemporary production it is more common for glass to be molded rather than cut into shape: in these stones the facets will be concave and facet edges rounded, and mold marks or seams may also be present. Glass has also been combined with other materials to produce composites. you need to be perfect Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... For Pb as an abbreviation, see Pb. ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... General Name, Symbol, Number thallium, Tl, 81 Chemical series poor metals Group, Period, Block 13, 6, p Appearance silvery white Atomic mass 204. ... Adoration, by Peter Paul Rubens. ... A scattering of brilliant cut diamonds shows off the many reflecting facets. ... For the province in the Philippines, see Antique (province) and for the band, see Antique (duo). ... Jewelry (the American spelling; spelled jewellery in Commonwealth English) consists of ornamental devices worn by persons, typically made with gems and precious metals. ... Conchoidal fracture describes the way that brittle materials break when they do not follow any natural planes of separation. ...

1900–1947

The first crystalline artificial diamond simulants were synthetic white sapphire (Al₂O₃, pure corundum) and spinel (MgO·Al₂O₃, pure magnesium aluminium oxide). Both have been synthesized in large quantities since the first decade of the 20th century via the Verneuil or flame-fusion process, although spinel was not in wide use until the 1920s. The Verneuil process involves an inverted oxyhydrogen blowpipe, with purified feed powder mixed with oxygen that is carefully fed through the blowpipe. The feed powder falls through the oxy-hydrogen flame, melts, and lands on a rotating and slowly descending pedestal below. The height of the pedestal is constantly adjusted to keep its top at the optimal position below the flame, and over a number of hours the molten powder cools and crystallizes to form a single pedunculated pear or boule crystal. The process is an economical one, with crystals of up to 9 centimeters (3.5 inches) in diameter grown. Boules grown via the modern Czochralski process may weigh several kilograms. Quartz crystal Synthetic bismuth crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules... Sapphire (from Hebrew: ספּיר Sapir) is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... Corundum (from Tamil kurundam) is a crystalline form of aluminium oxide and one of the rock-forming minerals. ... The spinels are any of a class of minerals which crystallize in the isometric system with an octahedral habit. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Standard atomic weight 24. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... The Verneuil process, also called flame fusion, is a method of manufacturing synthetic gemstones, developed in 1902 by the French chemist Auguste Verneuil. ... The 1920s is a decade sometimes referred to as the Jazz Age or the Roaring Twenties, usually applied to America. ... An oxyhydrogen flame is the flame attending the combustion of hydrogen and oxygen, and is characterized by a very high temperature. ... A blowgun or blowpipe is a simple weapon consisting of a small tube for firing light projectiles, or darts. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Silicon boule for the production of wafers. ... The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e. ...

Synthetic sapphire and spinel are durable materials (hardness 9 and 8) that take a good polish, but due to their much lower RI when compared to diamond (1.762–1.770 for sapphire, 1.727 for spinel) they are "lifeless" when cut. (Synthetic sapphire is also anisotropic, making it even easier to spot.) Their low RIs also mean a much lower dispersion (0.018 and 0.020), so even when cut into brilliants they lack the fire of diamond. Nevertheless synthetic spinel and sapphire were popular diamond simulants from the 1920s up until the late 1940s, when newer and better simulants began to appear. Both have also been combined with other materials to create composites. Commercial names once used for synthetic sapphire include Diamondette, Diamondite, Jourado Diamond', and Thrilliant. Names for synthetic spinel included Corundolite, Lustergem, Magalux, and Radient. This article or section does not adequately cite its references or sources. ...

1947–1970

The first of the optically "improved" simulants was synthetic rutile (TiO₂, pure titanium oxide). Introduced in 1947–48, synthetic rutile possesses plenty of life when cut—perhaps too much life for a diamond simulant. Synthetic rutile's RI and dispersion (2.8 and 0.33) are so much higher than diamond that the resultant brilliants look almost opal-like in their display of prismatic colors. Synthetic rutile is also doubly refractive: although some stones are cut with the table perpendicular to the optic axis to hide this property, merely tilting the stone will reveal the doubled back facets. Rutile in trellis texture characteristic of secondary rutile. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... 1947 (MCMXLVII) was a common year starting on Wednesday (the link is to a full 1947 calendar). ... 1948 (MCMXLVIII) was a leap year starting on Thursday (the link is to a full 1948 calendar). ... For other articles with similar names, see Opal (disambiguation). ...

The continued success of synthetic rutile was also hampered by the material's inescapable yellow tint, which producers were never able to remedy. However, synthetic rutile in a range of different colors, including blues and reds, were produced using various metal oxide dopants. These and the near-white stones were extremely popular if unreal stones. Synthetic rutile is also fairly soft (hardness ~6) and brittle, and therefore wears poorly. It is synthesized via a modification of the Verneuil process, which uses a third oxygen pipe to create a tricone burner—this is necessary to produce a single crystal, due to the much higher oxygen losses involved in the oxidation of titanium. The technique was invented by Charles H. Moore, Jr. at the South Amboy, New Jersey-based National Lead Company (later N. L. Industries). National Lead and Union Carbide were the primary producers of synthetic rutile, and peak annual production reached 750,000 carats (150 kg). Some of the many commercial names applied to synthetic rutile include: Astryl, Diamothyst, Gava or Java Gem, Meredith, Miridis, Rainbow Diamond, Rainbow Magic Diamond, Rutania, Titangem, Titania, and Ultamite. A dopant, also called doping agent and dope, is an impurity element added to a semiconductor lattice in low concentrations in order to alter the optical/electrical properties of the semiconductor. ... South Amboy is a City in Middlesex County, New Jersey, on the Raritan Bay. ... It has been suggested that this article be split into multiple articles. ... This article or section is incomplete and may require expansion and/or cleanup. ...

National Lead was also where research into the synthesis of another titanium compound, strontium titanate (SrTiO₃, pure tausonite), was conducted. Research was done during the late 1940s and early 1950s by Leon Merker and Langtry E. Lynd, who also used a tricone modification of the Verneuil process. Upon its commercial introduction in 1955, strontium titanate quickly replaced synthetic rutile as the most popular diamond simulant. This was due not only to strontium titanate's novelty, but to its superior optics: its RI (2.41) is very close to that of diamond, while its dispersion (0.19), although also very high, was a significant improvement over synthetic rutile's psychedelic display. Perhaps most importantly was the complete lack of yellow tint that so plagued synthetic rutile. Dopants were also used to give synthetic titanate a variety of colors, including yellow, orange to red, blue, and black. The material is also isotropic like diamond, meaning there is no distracting doubling of facets as seen in synthetic rutile. Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Atomic mass 87. ... // Recovering from World War I and its aftermath, the economic miracle emerged in West Germany and Italy. ... 1955 (MCMLV) was a common year starting on Saturday (link will display the full calendar) of the Gregorian calendar. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ...

Strontium titanate's only major drawback (if one excludes excess fire) is fragility. It is both softer (hardness 5.5) and more brittle than synthetic rutile—for this reason, strontium titanate was also combined with more durable materials to create composites. It was otherwise the best simulant around at the time, and at its peak annual production was 1.5 million carats (300 kg). Due to patent coverage all US production was by National Lead, while large amounts were produced overseas by Nakazumi Company of Japan. Commercial names for strontium titanate included Brilliante, Diagem, Diamontina, Fabulite, and Marvelite. A patent is a set of exclusive rights granted by a state to a patentee (the inventor or assignee) for a fixed period of time in exchange for the regulated, public disclosure of certain details of a device, method, process or composition of matter (substance) (known as an invention) which... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from...

1970–1976

From about 1970 strontium titanate began to be replaced by a new class of diamond imitations: the "synthetic garnets." These are not true garnets in the usual sense because they are oxides rather than silicates, but they do share natural garnet's crystal structure (both are cubic and therefore isotropic) and the general formula A₃B₂C₃O₁₂. While in natural garnets C is always silicon and A and B may be one of several common elements, most synthetic garnets are composed of uncommon rare earth elements. They are the only diamond simulants (aside from rhinestones) with no known natural counterparts: gemologically they are best termed artificial rather than synthetic, because the latter term is reserved for human-made materials that can also be found in nature. 1970 (MCMLXX) was a common year starting on Thursday. ... Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... It has been suggested that Silicons ranking be merged into this article or section. ... The periodic table of the chemical elements A chemical element, or element for short, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ... Rare earth ore Rare earth elements and rare earth metals are trivial names sometimes applied to a collection of 17 chemical elements in the periodic table, namely scandium, yttrium, and the lanthanides. ...

Although a number of artificial garnets were successfully grown, only two became important as diamond simulants. The first was yttrium aluminium garnet (YAG; Y₃Al₅O₁₂) in the late 1960s. It was (and still is) produced via the Czochralski or crystal-pulling process, which involves growth from the melt. An iridium crucible surrounded by an inert atmosphere is used, wherein yttrium oxide and aluminium oxide are melted and mixed together at a carefully controlled temperature of ca. 1980°C. A small seed crystal is attached to a rod which is lowered over the crucible until the crystal contacts the surface of the melted mixture. The seed crystal acts as a site of nucleation; the temperature is kept steady at a point where the surface of the mixture is just below the melting point. The rod is slowly and continuously rotated and retracted, and the pulled mixture crystallizes as it exits the crucible, forming a single crystal in the form of a cylindrical boule. The crystal's purity is extremely high, and it typically measures 5 cm (2 inches) in diameter and 20 cm (8 inches) long, and weighs 9,000 carats (1.75 kg). Yttrium aluminium garnet (YAG, Y3Al5O12) is a synthetic crystalline material of the garnet group, used as the active laser medium in various solid-state lasers. ... YAG Yttrium Aluminum Garnet Color: Wide range of colors Moh’s hardness: 8. ... The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... General Name, Symbol, Number iridium, Ir, 77 Chemical series transition metals Group, Period, Block 9, 6, d Appearance silvery white Atomic mass 192. ... Crucibles used in Czochralski method A crucible is a cup-shaped piece of laboratory equipment used to contain chemical compounds when heating them to very high temperatures. ... In English, to be inert is to be in a state of doing little or nothing. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Atomic mass 88. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... Bubbles in a soft drink each nucleate independently, responding to a decrease in pressure. ...

YAG's hardness (8.25) and lack of brittleness were great improvements over strontium titanate, and although its RI (1.83) and dispersion (0.028) were fairly low, they were enough to give brilliant-cut YAGs perceptible fire and good brilliance (although still much lower than diamond). A number of different colors were also produced with the addition of dopants, including yellow, red, and a vivid green which was used to imitate emerald. Major producers included ICT, INC. of Michigan, Litton Systems, Allied Chemical, Raytheon, and Union Carbide; annual global production peaked at 40 million carats (8,000 kg) in 1972, but fell sharply thereafter. Commercial names for YAG included Diamonair, Diamonique, Gemonair, Replique, and Triamond. For other uses, see Emerald (disambiguation). ... Raytheon Company (NYSE: RTN) is a major United States military contractor based in Waltham, Massachusetts. ... This article or section is incomplete and may require expansion and/or cleanup. ... 1972 (MCMLXXII) was a leap year starting on Saturday. ...

While market saturation was one reason for the fall in YAG production levels, another was the recent introduction of the other artificial garnet important as a diamond simulant, gadolinium gallium garnet (GGG; Gd₃Ga₅O₁₂). Produced in much the same manner as YAG (but with a lower melting point of 1750°C), GGG had an RI (1.97) close to, and a dispersion (0.045) nearly identical to diamond. GGG was also hard enough (hardness 7) and tough enough to be an effective gemstone, but its ingredients were also much more expensive than YAG's. Equally hindering was GGG's tendency to turn a dark brown upon exposure to sunlight or other ultraviolet source: this was due to the fact that most GGG gems were fashioned from impure material that was rejected for technological use. The SG of GGG (7.02) is also the highest of all diamond simulants and amongst the highest of all gemstones, which makes loose GGG gems easy to spot by comparing their dimensions with their expected and actual weights. Relative to its predecessors, GGG was never produced in significant quantities; it became more or less unheard of by the close of the 1970s. Commercial names for GGG included Diamonique II and Galliant. Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. ... Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... UV redirects here. ...

1976 to present

Cubic zirconia or CZ (ZrO₂; zirconium oxide—not to be confused with zircon, a zirconium silicate) quickly dominated the diamond simulant market following its introduction in 1976, and it remains the most gemologically and economically important simulant. CZ had been synthesized since 1930 but only in ceramic form: the growth of single-crystal CZ would require an approach radically different from those used for previous simulants due to zirconium's extremely high melting point (2750°C), unsustainable by any crucible. The solution found involved a network of water-filled copper pipes and radio frequency induction coils; the latter to heat the zirconium feed powder, and the former to cool the exterior and maintain a retaining "skin" under 1 millimeter thick. CZ was thus grown in a crucible of itself, a technique called cold crucible (in reference to the cooling pipes) or skull crucible (in reference to either the shape of the crucible or of the crystals grown). A round brilliant-cut cubic zirconia Cubic zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Standard atomic weight 91. ... Zircon is a mineral belonging to the group of nesosilicates. ... 1976 (MCMLXXVI) was a leap year starting on Thursday. ... Year 1930 (MCMXXX) was a common year starting on Wednesday (link is to a full 1930 calendar). ... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικός (keramikos). ... Crucibles used in Czochralski method A crucible is a cup-shaped piece of laboratory equipment used to contain chemical compounds when heating them to very high temperatures. ... Radio frequency induction or RF induction is an electrical phenomenon in which an electromagnetic wave passing through a conductor causes electric current to flow through it. ... The Skull Crucible process was developed at the Lebedev Physical Institute in Moscow to manufacture cubic zirconia. ...

At standard pressure zirconium oxide would normally crystallize in the monoclinic rather than cubic crystal system: for cubic crystals to grow, a stabilizer must be used. This is usually yttrium or calcium. The skull crucible technique was first developed in 1960s France, but it was perfected in the early 1970s by Soviet scientists under V. V. Osiko at the Lebedev Physical Institute in Moscow. By 1980 annual global production had reached 50 million carats (10,000 kg). In chemistry and other sciences, STP or standard temperature and pressure is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Atomic mass 88. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Standard atomic weight 40. ... The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... Soviet redirects here. ... The Lebedev Physical Institute of the Russian Academy of Sciences is a Russian research institute specializing in physics. ... Location Position of Moscow in Europe Government Country District Subdivision Russia Central Federal District Federal City Mayor Yuriy Luzhkov Geographical characteristics Area  - City 1,081 km² Population  - City (2007)    - Density 10,469,000   9684. ... 1980 (MCMLXXX) was a leap year starting on Tuesday. ...

The hardness (8–8.5), RI (2.15–2.18, isotropic), dispersion (0.058–0.066), and low material cost make CZ the best and most popular simulant of diamond. Its optical and physical constants are however variable, owing to the different stabilizers used by different producers. While the visual likeness of CZ is close enough to diamond to fool most who do not handle diamond regularly, CZ will usually give certain clues. For example: it is somewhat brittle and is soft enough to possess scratches after normal use in jewelry; it is usually internally flawless and completely colorless (whereas most diamonds have some internal imperfections and a yellow tint); its SG (5.6–6) is high; and its reaction under ultraviolet light is a distinctive beige. Most jewelers will use a thermal probe to test all suspected CZs, a test which relies on diamond's superlative thermal conductivity (CZ, like almost all other diamond simulants, is a thermal insulator). CZ is made in a number of different colors meant to imitate fancy diamonds (e.g., yellow to golden brown, orange, red to pink, green, and opaque black), but most of these do not approximate the real thing. Some CZs have been given a coating of diamond-like carbon in an effort to improve their durability, but this does not fool a thermal probe. UV redirects here. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... This article or section is in need of attention from an expert on the subject. ... Diamond-like carbon (DLC) is an umbrella term that refers to 7 forms[1] of amorphous carbon materials that display some of the unique properties of natural diamond. ...

CZ had virtually no competition until the 1998 introduction of simulated moissanite (SiC; synthetic silicon carbide). Simulated moissanite (synthetic silicon carbide) is superior to cubic zirconia in two ways: its hardness (8.5-9.25, see relative patents) and low SG (3.2). NOTE: All real moissanite is silicon carbide, but not all synthetic silicon carbide is real moissanite, hence the matter here. The former property results in facets that are as sometimes as crisp as a diamond's, while the latter property makes simulated moissanite (synthetic silicon carbide) somewhat harder to spot when unset (although still disparate enough to detect). Simulated moissanite (synthetic silicon carbide)is also more resistant to heat than any other jewel: so much so that it can be safely set directly into molten gold. However, its dispersion (0.104) is over twice that of diamond; it is also anisotropic with an RI of 2.648–2.691 and a high birefringence of 0.043. This manifests as the same "drunken vision" effect seen in synthetic rutile, although to a lesser degree. All simulated moissanite (synthetic silicon carbide) is cut with the table perpendicular to the optic axis in order to hide this property from above, but when viewed under magnification at only a slight tilt the doubling of facets (and any inclusions) is readily apparent. 1998 (MCMXCVIII) was a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean [1]. // Coated in ice, power and telephone lines sag and often break, resulting in power outages. ... Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ...

The inclusions seen in simulated moissanite (synthetic silicon carbide) are also characteristic: most will have fine, white, subparallel growth tubes or needles oriented perpedicular to the stone's table. It is conceivable that these growth tubes could be mistaken for laser drill holes that are sometimes seen in diamond (see diamond enhancement), but the tubes will be noticeably doubled in simulated moissanite (synthetic silicon carbide) due to its birefringence. Like synthetic rutile, current simulated moissanite (synthetic silicon carbide) production is also plagued by an as of yet inescapable tint, which is usually a brownish green. A limited range of fancy colors have been produced as well, the two most common being blue and green. Jewel-quality simulated moissanite (synthetic silicon carbide) is produced by only one company, Charles & Colvard. Its limited availability makes simulated moissanite (synthetic silicon carbide) about 120 times more expensive than cubic zirconia. This article addresses treatments designed to enhance the gemological characteristics of diamond. ...

When simulated moissanite (synthetic silicon carbide) was first introduced it made quite a stir: stories of widespread fraud were circulated by the press, with claims that simulated moissanite (synthetic silicon carbide) was indistinguishable from diamond even by experts. The aforementioned properties clearly demonstrate this to be false: the only people fooled by simulated moissanite were those who relied too heavily on thermal probes. This is because, like diamond, simulated moissanite (synthetic silicon carbide) has a high thermal conductivity; probes manufactured before simulated moissanite's (synthetic silicon carbide) introduction therefore registered simulated moissanite (synthetic silicon carbide) as diamond. More sophisticated thermal probes are now able to differentiate simulated moissanite (synthetic silicon carbide) from diamond, and Charles & Colvard also manufacture their own proprietary device which relies on simulated moissanite's (synthetic silicon carbide) greater opacity to ultraviolet light.

Natural simulants

Natural minerals that (when cut) optically resemble white diamonds are rare, because the trace impurities usually present in natural minerals tend to impart color. The earliest simulants of diamond were colorless quartz, topaz, and beryl (goshenite); they are all common minerals with above-average hardness (7–8), but all have low RIs and correspondingly low dispersions. Well-formed quartz crystals are sometimes offered as "diamonds," a popular example being the so-called "Herkimer diamonds" mined in Herkimer County, New York. Topaz's SG (3.50–3.57) also falls within the range of diamond. Minerals are natural compounds formed through geological processes. ... Quartz is one of the most common minerals in the Earths continental crust. ... Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. ... Three varieties of beryl: Morganite, Aquamarine, and Heliodor The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al2(SiO3)6. ... Herkimer diamonds from Fulton County, NY. Herkimer diamond is the misnomerous name for double-terminated quartz first discovered in exposed outcrops of dolostone at Little Falls in Herkimer County, New York and the Mohawk River Valley. ... Herkimer County is a county located in the state of New York. ...

From a historical perspective, the most notable natural simulant of diamond is zircon. It is also fairly hard (7.5), but more importantly shows perceptible fire when cut, due to its high dispersion of 0.039. Colorless zircon has been mined in Sri Lanka for over 2,000 years; prior to the advent of modern mineralogy, colorless zircon was thought to be an inferior form of diamond. It was called "Matara diamond" after its source location. It is still encountered as a diamond simulant, but differentiation is easy due to zircon's anisotropy and strong birefringence (0.059). It is also notoriously brittle and often shows wear on the girdle and facet edges. Zircon is a mineral belonging to the group of nesosilicates. ... Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on...

Much less common than colorless zircon is colorless scheelite. Its dispersion (0.026) is also high enough to mimic diamond, but although it is highly lustrous its hardness is much too low (4.5–5.5) to maintain a good polish. It is also anisotropic and fairly dense (SG 5.9–6.1). Synthetic scheelite produced via the Czochralski process is available, but it has never been widely used as a diamond simulant. Due to the scarcity of natural gem-quality scheelite, synthetic scheelite is much more likely to simulate it than diamond. A similar case is the orthorhombic carbonate cerussite, which is so fragile (very brittle with four directions of good cleavage) and soft (hardness 3.5) that it is never seen set in jewelry, and only occasionally seen in gem collections because it is so difficult to cut. Cerussite gems have an adamantine luster, high RI (1.804–2.078), and high dispersion (0.051), making them attractive and valued collector's pieces. Aside from softness, they are easily distinguished by cerussite's high density (SG 6.51) and anisotropy with extreme birefringence (0.271). Scheelite is a calcium tungstate mineral with the chemical formula CaWO4. ... In organic chemistry, a carbonate is a salt of carbonic acid. ... Sample of cerussite-bearing quartzite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and an important ore of lead. ...

Due to their rarity fancy-colored diamonds are also imitated, and zircon can serve this purpose too. Applying heat treatment to brown zircon can create several bright colors: these are most commonly sky-blue, golden yellow, and red. Blue zircon is very popular, but it is not necessarily color stable; prolonged exposure to ultraviolet light (including the UV component in sunlight) tends to bleach the stone. Heat treatment also imparts greater brittleness to zircon and characteristic inclusions.

Another fragile candidate mineral is sphalerite (zinc blende). Gem-quality material is usually a strong yellow to honey brown, orange, red, or green; its very high RI (2.37) and dispersion (0.156) make for an extremely lustrous and fiery gem, and it is also isotropic. But here again, its low hardness (2.5–4) and perfect dodecahedral cleavage preclude sphalerite's wide use in jewelry. Two calcium-rich members of the garnet group fare much better: these are grossularite (usually brownish orange, rarely colorless, yellow, green, or pink) and andradite. The latter is the rarest and most costly of the garnets, with three of its varieties—topazolite (yellow), melanite (black), and demantoid (green)—sometimes seen in jewelry. Demantoid (literally "diamond-like") especially has been prized as a gemstone since its discovery in the Ural Mountains in 1868; it is a noted feature of antique Russian and Art Nouveau jewelry. Titanite or sphene is also seen in antique jewelry; it is typically some shade of chartreuse and has a luster, RI (1.885–2.050), and dispersion (0.051) high enough to be mistaken for diamond, yet it is anisotropic (a high birefringence of 0.105–0.135) and soft (hardness 5.5). Sphalerite sample Another sphalerite sample The unit cell of sphalerite Sphalerite (ZnS) is a gay mineral that is the chief ore of zinc. ... Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ... The garnet group of minerals show crystals with a habit of rhombic dodecahedrons and trapezohedrons. ... Andradite is a kind of garnet. ... Topazolite is a variety of andradite. ... Melanite is a mineral, a depp, glossy black form of garnet containig Titanium. ... Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet family of minerals. ... Map of the Ural Mountains The Ural Mountains (Russian: , Uralskiye gory) (also known as the Urals, the Riphean Mountains in Greco-Roman antiquity, and known as the Stone Belt) are a mountain range that runs roughly north and south through western Russia. ... 1868 (MDCCCLXVIII) was a leap year starting on Wednesday (see link for calendar) of the Gregorian calendar or a leap year starting on Friday of the 12-day-slower Julian calendar. ... Vitebsk Railway Station one of the finest examples of Art Nouveau architecture. ... Titanite Titanite or sphene is a calcium titanium nesosilicate mineral, CaTiSiO5. ...

Discovered the 1960s, the rich green tsavorite variety of grossular is also very popular. Both grossular and andradite are isotropic and have relatively high RIs (ca. 1.74 and 1.89, respectively) and high dispersions (0.027 and 0.057), with demantoid's exceeding diamond. However, both have a low hardness (6.5–7.5) and invariably possess inclusions atypical of diamond—the byssolite "horsetails" seen in demantoid are one striking example. Furthermore, most are very small, typically under 0.5 carats (100 mg) in weight. Their lusters range from vitreous to subadamantine, to almost metallic in the usually opaque melanite, which has been used to simulate black diamond. Some natural spinel is also a deep black and could serve this same purpose. The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... Tsavorite or tsavolite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca3Al2Si3O12)[2] Trace amounts of vanadium or chromium provide the green color. ... Well-cleaved, dark, fine-grained chlorite-actinolite metadiabase intrudes light granitic gneiss Actinolite is an inosilicate mineral with the chemical formula Ca2(MgFe)5Si8O22(OH)2 // Mineralogy Actinolite is an intermediate member in a series between tremolite (Mg-rich) and ferro-actinolite (Fe-rich). ...

Composites

Because strontium titanate and glass are too soft to survive use as a ring stone, they have been used in the construction of composite or doublet diamond simulants. The two materials are used for the bottom portion (pavilion) of the stone, and in the case of strontium titanate, a much harder material—usually colorless synthetic spinel or sapphire—is used for the top half (crown). In glass doublets, the top portion is made of almandine garnet; it is usually a very thin slice which does not modify the stone's overall body color. There have even been reports of diamond-on-diamond doublets, where a creative entrepreneur has used two small pieces of rough to create one larger stone. Almandine, or almandite, is a name applied to certain kinds of precious garnet, being apparently a corruption of alabandicus, which is the name applied by Pliny to a stone found or worked at Alabanda, a town in Caria in Asia Minor. ...

In strontium titanate and diamond-based doublets, an epoxy is used to adhere the two halves together. The epoxy may fluoresce under UV light, and there may be residue on the stone's exterior. The garnet top of a glass doublet is physically fused to its base, but in it and the other doublet types there are usually flattened air bubbles seen at the junction of the two halves. A join line is also readily visible whose position is variable; it may be above or below the girdle, sometimes at an angle, but rarely along the girdle itself. Epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United...

The most recent composite simulant involves combining a CZ core with an outer coating of laboratory created amorphous diamond. The concept effectively mimics the structure of a cultured pearl (which combines a core bead with an outer layer of pearl coating), only done for the diamond market. Brought to market under the 'Asha' brand name, the finished simulant provides a more lustrous and diamond-like look than plain CZ due to its usage of amorphous diamond.

See also

• Diamond enhancement
• Diamond color
• Diamond cut
• Diamond clarity
• Material properties of diamond
• Synthetic diamond

This article addresses treatments designed to enhance the gemological characteristics of diamond. ... Jewelers set diamonds in groups of similar colors. ... In order to best utilize a diamond gemstones superlative material properties, a number of different diamond cuts have been developed. ... Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal defects of a diamond called inclusions, and surface defects called blemishes. ... This article addresses the material properties of diamond. ... A colourless synthetic diamond produced via chemical vapour deposition Synthetic diamond is a diamond produced through chemical or physical processes in a factory. ...

References

• Hall, Cally. (1994). Gemstones, p. 63, 70, 121. Eyewitness Handbooks; Kyodo Printing Co., Singapore. ISBN 0-7737-2762-0
• Nassau, Kurt. (1980). Gems made by man, pp. 203–241. Gemological Institute of America; Santa Monica, California. ISBN 0-87311-016-1
• O'Donoghue, Michael, and Joyner, Louise. (2003). Identification of gemstones, pp. 12–19. Butterworth-Heinemann, Great Britain. ISBN 0-7506-5512-7
• Pagel-Theisen, Verena. (2001). Diamond grading ABC: The manual (9th ed.), pp. 298–313. Rubin & Son n.v.; Antwerp, Belgium. ISBN 3-9800434-6-0
• Schadt, H. (1996). Goldsmith's art: 5000 years of jewelry and hollowware, p. 141. Arnoldsche Art Publisher; Stuttgard, New York. ISBN 3-925369-54-6
• Webster, Robert, and Read, Peter G. (Ed.) (2000). Gems: Their sources, descriptions and identification (5th ed.), pp. 65–71. Butterworth-Heinemann, Great Britain. ISBN 0-7506-1674-1