DDG Ass #16 Lab Grown Diamonds PDF

DDG Ass #16 : Lab Grown Diamonds History of Lab Grown Diamonds: - Two major commercial technologies are used to produce lab-grown diamonds: the high-pressure, high- temperature (HPHT) method and the chemical vapor deposition (CVD) method. - Both developed over the last 75 years and were once used o...

DDG Ass #16 : Lab Grown Diamonds History of Lab Grown Diamonds: - Two major commercial technologies are used to produce lab-grown diamonds: the high-pressure, high- temperature (HPHT) method and the chemical vapor deposition (CVD) method. - Both developed over the last 75 years and were once used only to produce diamonds for industrial purposes Early History: -In 1797, English chemist Smithson Tennant published his research proving that diamond were dense pure carbon -In the 1800s and early 1900s, many researchers and chemists tried to create diamond, but did have the technology to pull it off -In 1941, Percy W. Bridgman, an American researcher in high-pressure physics, was hired by the General Electric Corporation (GE), no diamonds were made but advance in high pressure technology -In 1952, scientists began experimenting with a different approach to diamond growth. William G. Eversole was able to produce tiny diamonds using the CVD growth method - GE scientists created their first batch of industrial diamonds using the HPHT method in December 1954, and after confirming the process they announced there achievement in 1955 First Gem Quality: - Early progress in creating large gem-quality diamonds was limited. Larger crystals take much longer to form than tiny ones. - The GE research team worked on addressing these issues, and in 1970 they produced the first cuttable gem-quality HPHT lab-grown diamonds, weighing about 1 carat each in rough form. Fashioned stones cut from those crystals ranged from 0.26 to 0.46 ct. and F - J in color, highest clarity is VS, along with yellow and blue colors - In the 1990s, Japan’s Sumitomo Electric Industries, GE, and De Beers began to produce larger, near- colorless HPHT diamonds and marketed for use in high-tech applications and for experimental use only - 1993, the largest reported HPHT lab-grown diamond crystal weighed 34.80 cts. and took 600 hours—25 days with only some areas of the rough were gem quality - As the technology to produce gem-quality diamonds became known, a small number of manufacturers in the U.S., China, Russia, and the Ukraine began to market them to the jewelry industry. - By 2003, the jewelry industry was beginning to accept lab-grown diamonds as a commercial product. HPHT diamonds of 2.5 to 3.5 cts. were being produced in commercial quantities in a variety of colors, such as yellow, blue, green, and pink. - In 2003, gem-quality lab-grown diamonds were produced for jewelry using the CVD method. They were predominantly brown, and often small due to the rough material's limited thickness. - However, by 2007 they were able to produce a variety of colors, including colorless to near-colorless, orange to pink, and brown. Recent Break Throughs: - In 2014, a Russian manufacturer, New Diamond Technology (NDT), began to produce large colorless faceted HPHT diamonds up to 5.11 cts. - Then, in 2015, NDT produced a colorless, VS clarity, 10.02-ct. faceted HPHT diamond. - The as-grown rough was 32.26-ct. NDT was the first to produce a colorless to near-colorless lab-grown diamond above 10 carats in faceted weight. - In November 2018, NDT announced the creation of a 55.94-ct. HPHT diamond. Once faceted, the diamond weighed 20.22 cts. and had orange color and VS clarity, - That same year, NDT announced the largest HPHT lab-grown diamond to date: an astonishing 103.5-ct. rough crystal grown in 14 days. - Equipment capacity, growth time, and costs are some factors that lab-grown diamond producers must consider. - Industrial Applications of Lab Grown Diamonds: -Tools embedded with natural or lab-grown diamonds are used for machining automotive components. Some are designed for cutting natural hardwoods, granite, and marble. They’re embedded into drill bits, machining tools, and saws. They’re also used to engrave fine glassware and as scalpels for delicate surgeries, -"Slices” of large single-crystal lab-grown diamonds are used for industrial and surgical tools, laser windows, and heat sinks -Scientific advances have made lab-grown diamonds better than natural diamonds for many industrial uses due to the level of control they have to eliminate imperfections and produce specific shapes The High Pressure , High Temperature Method : HPHT Synthesis: - The high-pressure, high-temperature method replicates the earth’s natural process by using high temperature and high pressure to grow a diamond in the laboratory. -HPHT lab-grown diamonds are produced by converting a carbon source, such as graphite or diamond powder, to diamond by using a HPHT press. -Grown with pressures of about 5 to 6 GPa (about 50 to 60 kilobars), equivalent to a 150–190 km depth in the earth. Temperatures reach about 1300°C to 1600°C. -Depending on the desired size, HPHT diamonds can take anywhere from a couple days to weeks to grow. - A molten metal catalyst is used to slightly lower the temperatures and pressures necessary for diamond growth, which increases the rate of chemical reaction. -For HPHT diamonds, the catalyst is usually a mixture of iron, nickel, cobalt, and titanium or other elements -HPHT press designs main difference is how many anvils—the pressure-applying components—are used. - An early HPHT tetrahedral hydraulic diamond press ("the Belt") was invented by H. Tracy Hall. GE used it to produce its first lab-grown diamond in 1954. -Today the cubic, BARS, and toroid presses are common in the industry. -The cubic press is the most common press used by Chinese manufacturers. -The BARS and toroid presses are both Russian designs. The BARS press is more compact, based on a split sphere with eight outer anvils. The toroid press uses only two anvils. -The type of press, the growth chambers—or cells—of the press have similar components. The larger the cell, the larger the potential size of the diamond produced. -However, a larger cell requires greater pressure to create diamond. The pressure produced by the different presses depends on the number of anvils and their diameter. -The larger the diameter, the more pressure the press can produce. -The HPHT process requires a carbon source, heating element, metal catalyst, seed crystal, and temperature gradient. -The carbon source area of the growth chamber is hotter than the area that holds the seed crystal at the bottom of the chamber. -Small HPHT crystals or “grit” are used as the diamond seed. -One or more crystals can be grown at the same time based on press and chamber design. HPHT Lab Grown Diamond Supply Landscape: -China's first HPHT lab-grown diamond was produced in 1963. China is now the world’s largest producer of HPHT lab- grown industrial diamonds,2016 production of about 20 billion carats accounted for 98 percent of the global supply. -HPHT diamond melee production is also quickly becoming a large industry in China. Factories full of HPHT presses are found in the city of Zhengzhou. Rough Crystal Form: - HPHT diamond forms along different crystallographic directions at different rates. In these diamond crystals, growth is predominantly cuboctahedral: the crystals have both octahedral and cubic faces. - A cuboctahedron looks like a broad-based, tapered pyramid terminated by a small flat face. This shape is never seen in a natural diamond. -A growth sector is a three-dimensional region with a common crystallographic growth plane. -Defects can sometimes help you locate a particular growth sector only seen in lab-grown diamonds, and therefore help with identification. Diamond Types: -Atomic impurities such as nitrogen and boron readily incorporate into a growing HPHT lab-grown diamond. -When nitrogen is present, it is incorporated in the crystal lattice as isolated nitrogen resulting in type Ib and yellow in color, a diamond type rare in nature -Even if the lab-grown diamond is heated to high temperatures, isolated nitrogen is extremely difficult to remove completely. The isolated nitrogen gives these diamonds a yellow color. -Growing colorless HPHT diamonds is significantly more difficult. The components in the chamber must be of very high purity, and any nitrogen-containing air bubbles must be removed. -Producers must change the growth chemistry and include “nitrogen getters”—elements such as aluminum and titanium that have a strong affinity to nitrogen—which effectively trap the nitrogen and prevent it from incorporating into the diamond. -The resulting colorless HPHT diamonds are type IIa or weak type IIb (not enough boron to induce a blue color). Identification: - The vast majority of distinctive growth features in HPHT lab-grown diamonds are due to the cuboctahedral arrangement of internal growth sectors, as well as inclusions from the metal catalyst. - A trained gemologist can identify some HPHT diamonds using standard gemological instruments and three basic procedures: Examining the diamond with a microscope Checking for strain Checking the diamond’s fluorescence under ultraviolet (UV) radiation Microscopic Examination: - HPHT diamonds might contain remnants of the metal catalyst they grew in. Some surface-reaching inclusions, such as feathers and chips, can be seen in both natural and HPHT diamonds. - Large metallic inclusions often appear dark in transmitted light and are typically rounded, elongated, or irregularly shaped. - Sparse metallic pinpoint inclusions may also be observed in HPHT diamonds and are most clearly seen in type Ib yellows. -crystal growth structures like graining and color zoning remain in the fashioned stone. These features can help identify a gem as lab-grown or natural.crystal growth structures like graining and color zoning remain in the fashioned stone. These features can help identify a gem as lab-grown or natural. - laboratory diamonds to grow cuboctahedrally. The growth sectors related to the cubic and octahedral crystal faces of an HPHT diamond can create a distinctive graining pattern. Graining is often visible in colored HPHT diamonds through the pavilion under magnification. -color zoning in colored lab-grown diamonds also follows the stone’s growth patterns. Observing Strain: - A polarizer, or polarizing filter, is a plastic disk embedded with specifically oriented microscopic crystals, designed to transmit polarized light. - Looking for strain requires two polarizers, one above the other. One filter is stationary, and the other is rotated so its light-transmitting direction is perpendicular—at a 90-degree angle—to the other filter’s light- transmitting direction, blocking the light- This is referred to as crossed polarizers or the dark position. -If there is strain, some light will be transmitted through the second polarizing filter, creating a visible pattern. - The more heavily strained the diamond is, the clearer the patterns are, with bright interference colors dominating, such as red, pink, orange, yellow, and green. - Interference colors are caused by the interaction of two light rays and can be seen only under cross-polarized light. - HPHT diamonds never show clear strain patterns. They show only subdued interference colors, such as white, gray, or black. UV Luminescence: - HPHT lab-grown diamonds generally show a stronger fluorescence reaction to shortwave UV than to longwave UV -However, the vast majority of colorless HPHT diamonds exhibit no detectable fluorescence to longwave UV. When fluorescence is detected, its color is generally greenish yellow to yellow under shortwave UV and yellow to orange under longwave UV. -Some HPHT diamonds are phosphorescent: Their fluorescent glow remains for a short time after the shortwave UV radiation is turned off. - Blue and colorless HPHT diamonds often show green-blue phosphorescence caused by the presence of boron. The Chemical Vapor Method: - Single-crystal, gem-quality CVD lab-grown diamond was once considered a “holy grail” within the research community -Unlike HPHT lab-grown diamonds, CVD lab-grown diamonds are grown under conditions in which there is a low probability of forming diamonds. However, once a diamond forms, tremendous energy is required to break the atomic bonds. CVD Synthesis: -CVD growth occurs at very low pressures and moderate temperatures (compared to natural and HPHT growth), where the stable form of carbon is graphite. - Metastable means that diamond is theoretically unstable but regarded as stable due to its longevity. - CVD diamonds are grown in heated mixture of a hydrocarbon gas (such as methane) & excess hydrogen gas - Growing diamonds using the CVD process requires a gaseous carbon source, hydrogen gas, substrate, energy source, and heating element. -Within the vacuum chamber, a substrate is used as a template or seed for new diamond growth. -The substrate can be natural or lab-grown, although typically CVD or HPHT diamonds are used as substrates. -Gases flow through the chamber and are activated by an energy source (typically a microwave plasma), which breaks apart the gas molecules to release carbon atoms. Rough Crystal Form: - CVD lab-grown diamonds form layer by layer in conditions in which they normally wouldn’t be stable -CVD diamond deposition on the substrate occurs mainly through perpendicular and lateral microscopic growth creating growing surfaces consisting of a series of steps, or growth sectors, known as terraces and risers. - Polycrystalline diamond can happen and is made up of many small diamond crystals interlocking together as they grow. In CVD environments it is usually opaque and black. The only solution is to stop the growth process, remove the crystal from the reactor, and polish away the polycrystalline material. -CVD lab-grown diamond crystals resemble slabs with a square cross section. - CVD diamonds come out of the reactor, the edges are covered in black graphite and polycrystalline material. and go through laser treatment to produce a square or tubercular shape Diamond Types : -the majority of CVD lab-grown diamonds are type IIa. - Growing colorless to near-colorless CVD diamonds is difficult, expensive, and slow. - Adding very low concentrations of nitrogen or oxygen to the gas mixture results in faster growth but that can create a brown color -HPHT treatment can remove the brown color of as-grown CVD diamond. -The vast majority of colored CVD diamonds are within the pink range. Their hues include a variety of colors, such as pinkish brown, brownish pink, pink, purplish pink, and orangy pink. Hybrid Material: -A small number of natural diamonds have been enhanced with CVD overgrowth this case a natural diamond substrate is used and left in the finished stone—and usually makes up the majority of it. This can add weight to the natural diamond or even change its face-up color. Identification: - Most CVD lab-grown diamonds cannot be identified using standard gem-testing equipment and must be submitted to a laboratory for identification. -A trained gemologist may be able to identify these indications using standard gemological equipment and these three basic procedures: Examining the diamond with a microscope Checking for strain Checking the diamond’s fluorescence under UV radiation Microscope Examination: - Most CVD lab-grown diamonds are often high in clarity. -Those that have inclusions typically have black graphitic inclusions of various sizes, or tiny pinpoints of non- diamond carbon (most less than 50 µm) that cluster together to form clouds. - If the CVD diamond was HPHT treated, there may be radial fractures around the inclusions as well. - As with HPHT lab-grown diamonds, major CVD lab-grown diamond manufacturers often inscribe the origin on the girdle Observing Strain: - CVD lab-grown diamonds form without the stabilization of high pressures, they often have strain. -CVD lab-grown diamonds show irregular or mottled patterns with both bright and subdued interference colors. -The presence of strain can help separate a CVD diamond from an HPHT diamond. UV Luminescence: - As-grown near-colorless to colorless CVD diamonds are usually inert under longwave and shortwave UV or fluoresce yellow or orange if at all. -HPHT-treated CVD diamonds can fluoresce very weak to moderate green under shortwave UV. -CVD diamond’s growth sectors and possible growth interruptions can be identified using a DiamondView. - Disruptions during growth cause the interruption lines to fluoresce distinctly. Lab Grown Diamonds in the Marketplace: - The lab-grown diamond value chain or pipeline is similar to the mined diamond value chain. -the value chain has the same downstream segments: cutting and polishing, polished diamond sales, jewelry manufacturing, and retail. Disclosure: - In August 2018, the U.S. Federal Trade Commission (FTC) amended its publication Guides for the Jewelry, Precious Metals, and Pewter Industries. -The FTC may take action under Section 5 of the FTC Act, which prohibits deceptive or unfair acts or practices, if a marketer or other industry member makes a claim inconsistent with the Guides. -In November 2019, the World Jewellery Confederation (CIBJO) formed the Laboratory-Grown Diamond Committee to establish operating practices for the lab-grown diamond trade Screen Device Service: - HPHT and CVD methods can produce large high-quality diamonds in various colors. More and more HPHT lab-grown melee diamonds are also entering the trade and creating concern in the industry. -Most diamond screening devices are based on the fact that the majority of natural diamonds are type Ia. -It is important to understand the limitations of a screening device and what a “pass” or “refer” means for that device. -However, if you are not certain of a stone’s identity, submit it to a gemological laboratory for identification. Lab Grown Grading Report: - n 2007, GIA began to offer a report service for lab-grown diamonds called the Synthetic Diamond Grading Report -Lab-grown diamonds are plotted the same way as natural diamonds, but because of the lab-grown nature of some inclusions, other terms are used to describe these features. - “Growth remnant” is used in place of a crystal, needle, cloud, or pinpoint. “Crystal surface” and “indented crystal surface” are used in place of a natural and an indented natural.