Distinguishing Natural Diamonds from Synthetic Diamonds and Diamond

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Synthetic Diamond Identification About GIA Knowing the Difference Because of the contrasting conditions of natural Established in 1931, GIA has studied the scientific Natural diamonds have long fascinated mankind and artificial formation, synthetic diamonds properties of gems, developing new methods of with their unique physical and visual properties. display several features which allow them to be identifying natural, synthetic and treated gemstones. Distinguishing Features such as exceptional hardness, durability, gemologically distinguished from natural diamonds. This research serves to protect all who buy and sell light reflectivity (brilliance) and dispersion (fire) These include visual characteristics such as color gems by ensuring accurate and unbiased standards Natural Diamonds from distinguish them from other gems. The beauty and zoning, dark metallic inclusions, weak strain for determining and describing gem quality. GIA universal appeal of natural diamonds come at a patterns and distinctive patterns and colors of research findings are incorporated into its educational Synthetic Diamonds and price, as the recovery and fashioning of such rare ultraviolet fluorescence. Because they represent programs, published in professional journals, used for Diamond Simulants gems are challenging. For decades, researchers types of diamonds that are rare in nature, synthetic developing practical instruments and tools and applied have sought alternatives by creating less expensive diamonds also possess additional features that in grading and identification services every day. “look-alikes” in the form of simulants and, more can be detected with gemological instruments. recently, “duplicates” with synthetic diamonds. To learn more about diamond identification and Though such attempts by man to recreate the Decades of research, in addition to the use and GIA laboratory services, and to view past issues of properties and structure of natural diamonds are development of advanced scientific instrumentation, Gems & Gemology, visit GIA.edu nothing new, a rapid increase in synthetic diamond enable GIA to accurately identify synthetic growth technology over the past decade has led diamonds. GIA’s Diamond Check™ and recent to real concerns regarding their identification. introduction of a fully automated Melee Analysis Service allow for fast and accurate separation Fortunately, GIA has followed the developments of of loose natural diamonds from loose synthetics synthetic diamonds for more than 60 years. This and simulants. The challenge to develop a similar continuum—combined with fundamental research method for analysis of mounted stones is more on tens of millions of natural diamonds—allows complex due to coverage from metal settings. GIA to accurately identify synthetic diamonds. Information on synthetic diamond identification In order to protect yourself and your clients has been published extensively in GIA’s peer- against misrepresentations and misconceptions reviewed Gems & Gemology over the last 30 years. surrounding natural diamonds, synthetic diamonds, and diamond simulants, it is important that you understand the differences among them and the means of their identification. Unlike diamond simulants, which can be recognized by using standard gem testing, synthetic diamonds have essentially the same chemical composition and crystal structure as natural diamonds, but are made in laboratories—not grown in the earth. Because their optical and physical properties are nearly identical to natural diamonds’, identifying synthetic diamonds is complex. However, because of their artificial growth environments, synthetic diamonds exhibit several diagnostic features that allow for their detection in gemological laboratories.

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The World’s Foremost Authority in Gemology synthetic diamond (middle) and simulant (bottom). diamond (top), image: Natural cover Front

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Natural diamonds are a wonder of science, Following their extended time in residence in the Although their use for jewelry purposes is a somewhat Various materials have been used as imitations or as they occur only when atoms of carbon are mantle, some diamonds are brought to the earth’s recent occurrence, synthetic diamonds have been substitutes for diamonds since ancient times. These exposed to high pressures and temperatures surface by volcanic eruptions of kimberlite magma. produced for industrial applications since the 1950s. materials, often referred to as diamond simulants, about 100 miles (160 kilometers) below the earth’s Geologists believe that the diamonds are transported Unlike natural diamonds, synthetic diamonds are may grow naturally in the earth or artificially in surface in what geologists call the upper mantle. by the magma very quickly over the 100-mile distance grown in laboratories, over a very short period of a lab. Years ago, the colorless varieties of some Diamond crystals reside in these extreme mantle (in just a week or more), so that the diamonds are not time – likely just two or three weeks (or less). A colored stones (i.e., quartz) were used to simulate conditions for millions of years. The crystals physically changed in the process and transformed to longer growth period results in larger crystals; diamond. Today, the most common simulants are that grow under these conditions have a unique graphite. During this rapid upward journey, the diamond however, steady environmental conditions must be cubic zirconia (zirconium oxide, or CZ), and to a structure we associate with natural diamonds. crystal can, however, break along cleavage directions, maintained to ensure the formation of high-quality lesser extent, synthetic moissanite (silicon carbide). and undergo other changes that may affect, for crystals. Currently, the production of synthetic Because simulants differ completely from diamond, Natural diamond crystals sometimes incorporate solid diamonds in melee sizes is what is most encountered. example, its color. they display diagnostic properties by which they small inclusions of diamonds or other minerals into The drastically shorter growth period of synthetic can be recognized with standard gem testing their structure as they grow. While mineral inclusions diamonds results in features that are of diagnostic techniques, observations under magnification are often considered a negative clarity feature in a value in separating them from natural diamonds. and commercially available “diamond testers.” polished diamond, they are of tremendous value to Two artificial growth methods are used to create geoscientists. Natural diamonds provide a way for synthetic diamonds: HPHT and CVD. HPHT (high these mineral inclusions to be preserved and brought pressure/high temperature) synthesis, developed in to the earth’s surface where they can be scientifically the 1950s, uses high temperatures and pressures, a studied. Because certain inclusions contain radioactive molten metal flux and a diamond seed to initiate crystal elements that decay at a known rate, the minerals can formation. The result is a distinctive crystal shape which also be used to calculate the age of diamond formation. is a combination of octahedral and cube faces and a flat base. The HPHT process more closely mirrors the conditions of natural diamond formation than CVD. The CVD (chemical vapor deposition) method, which Volcanic chain A natural diamond is a gift from the earth. A cutter carefully examines the rough was mostly developed during the past decade, produces Mid-ocean ridge Subduction zone before polishing to a finished gem of optimal beauty. Courtesy: Aftergut N. & Zonen. Antwerp, Belgium diamonds through the use of low pressures and high temperatures Mobile belt in a vacuum chamber. A carbon- 140 km Graphited Diamond simulants, from top (left to right): Strontium titanate, synthetic spinel, Craton Diamon containing gas such as methane is synthetic rutile, yttrium aluminum garnet (YAG), zirconium oxide (CZ), zircon. UPPER MANTLE introduced into the chamber, and gas 410 km molecules break down there into the l Mantle keel with TRANSITION ZONE ithospheric diamonds constituent atoms. The carbon atoms 660 km “rain” down onto flat diamond seed LO plates, resulting in a square-shaped, WER MANTLE Mantle plum Rough colorless HPHT 900 km e tabular synthetic diamond crystal. synthetic crystals.

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KimberlitKimberliteeBasalBasalt/Eclogitet/Eclogite LithosphericLithospheric mantle mantle ConvectingConvecting mantle mantle

This block diagram depicts the basic relationship between a continental craton, its lithospheric mantle keel, and diamond stability regions in the keel and the convecting mantle. Under the right conditions of low oxidation, diamonds can form in the convecting mantle, the subducting slab, and in the majority of cases, in the mantle keel. Courtesy: Steven B. Shirey, modified from R. Tappert and M.C. Tappert, Diamonds in Nature: A Guide to Rough Diamonds (2011) Natural Diamond Synthetic Diamond Cubic Zirconia

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