One need to know the enemy’s face in order to resist him – this is the rule of life which can also be applied to diamonds. Though synthetic diamonds are far from being enemies but rather customer-, pocket- and environment-friendly gems, it’s better to have thorough knowledge of them.
The case of 600 undisclosed synthetic diamonds made a huge stir this year. On the one hand, this case which everybody hopes is simply an isolated accident shows how easily a diamond buyer can be cheated, but on the other, it highlights exceptional properties of synthetic diamonds. We have already mentioned about the unique technologies used to grow diamonds (HPHT and CVD), but since the issue of synthetic diamonds is hotly discussed today it’s better to know more about them. So go on reading to find our some details concerning diamond growing and grown diamonds themselves:
Synthetic stones are currently made from two methods: High Pressure-High Temperature (HPHT) and Chemical Vapor Deposition (CVD). While “both methods can produce
gem-quality diamonds and both are costly and challenging,” says Thomas M. Moses, senior vice president of Gemological Institute of America’s (GIA) Laboratory and Research Department, the processes used and the types of synthetic stones created by the two methods vary greatly in their characteristics.
HPHT, explains Moses, was “originally introduced by General Electric in 1954, and mimics the intense heat and pressure that — over millions of years — crystalizes carbon into natural diamonds.” These synthetic stones are made in a press that is able to generate these extreme conditions. The first such apparatus, developed by General Electric, was called a “Belt Press,” and today there are many variations of this model, which vary in size and capability. Each press has a growth chamber where HPHT stones are grown from carbon molecules in a metallic solvent catalyst that is usually made up of iron, nickel or a mixture of the two.
“On average,” says Moses, “the growth time for a 1-carat HPHT synthetic diamond is approximately one week, but because of the small size of the growth chamber, only a few can be produced at a time.” Due to this drawback, and the economics of production and scale, most HPHT stones are around .50 carats in size. However, “in rare instances, rough synthetic diamonds up to 4 carats are being grown; when faceted, they can produce cut diamonds of about 2 carats,” notes Moses.
While the HPHT method has been around for half a century, its profitability was established only relatively recently. “The HPHT process, even though known since
the 1950s, has taken many years to evolve into a commercially viable process. Until
nearly a decade ago, the price of HPHT-grown diamonds was simply too high,”
CHARACTERISTICS OF HPHT STONES
Diamonds are scientifically classified by type based on the amount and location of the impurities they contain. Almost all HPHT stones are type Ib, with up to.05 percent nitrogen dispersed throughout the diamond. This type of diamond accounts for less than 1 percent of all natural stones. Among natural stones, 98 percent are type Ia, stones containing up to
.30 percent of nitrogen found in concentrated clusters. A small percentage of HPHT stones are type Iaa, in which scattered nitrogen atoms are found in pairs.
Because the nitrogen in HPHT stones is scattered and dispersed, almost all these stones have an identifiable color. “The majority of HPHT goods produced so far are in the color grades from H to P — the trace of single nitrogen atoms is responsible for this yellowish, brownish tint,” explains Hainschwang.
On a microscopic level, HPHT stones are also inherently shaped differently than natural ones. “The HPHT growth method typically produces cube-octahedral-like crystals, which is a different shape than natural diamond crystals,” says Moses.
Because they are grown in metallic solvents of iron or nickel, the majority of HPHT stones have metal inclusions, which usually show up as visible black spots on the stone and cause the diamond to exhibit strong magnetism. While some natural diamonds may also exhibit magnetism, they are of much lower levels than those created through the HPHT process.
The CVD method differs greatly from HPHT in that “synthetic diamonds are produced by using microwaves or other sources of energy to break down hydrocarbon gas, such as methane, inside a vacuum chamber. This causes carbon atoms to accumulate in thin layers on a flat diamond substrate — similar to the way snowflakes accumulate in a snowfall,” explains Moses.
The substrate used in the process, which is placed in a reaction chamber, is always a carbon source, either an HPHT-grown synthetic or a piece of graphite. The process, however, is a slow one as only .10 millimeters (mm), or 100 microns of diamond can be grown per hour. This growth also has its limits in terms of depth. CVD stones over 3 mm in thickness are extremely difficult to grow.
The CVD method, which was first successfully tried by Houston, Texas–based chemical manufacturer Union Carbide Corporation in the 1950s, “is less costly and challenging than HPHT because it works at moderate temperatures and low pressure, requiring smaller and less costly equipment,” says Moses.
Like HPHT, the CVD method has only recently become economically viable. “CVD synthesis capability has advanced noticeably over the past five years, and we are now witnessing the emergence of a small number of start-up companies that are attempting to commercialize production of CVD for gem applications,” notes Simon Lawson, head of research and development at the DTC Research Centre, based in Maidenhead, U.K., which offers identification services for synthetic and treated diamonds and researches new techniques and methods of detection.
CHARACTERISTICS OF CVD STONES
Due to their unique growth processes, CVD stones are type IIa, which contain negligible amounts of nitrogen and have high thermal conductivity. CVD stones are also differentiated by their shape. “The CVD method,” says Moses, “produces flat, tabular synthetic diamond crystals, which are different than natural diamond crystals.”
Because of the difficulty and cost of growing CVD stones over 3 mm thick, almost all CVD stones are smaller than 1 carat. Indeed, the largest gem-quality CVD stone ever produced was 1.05 carats, grown by now-defunct synthetic manufacturer Apollo Diamond in 2010. Although CVD stones do not contain metal or nitrogen, they still have a distinct color due to the gases used in the CVD process. “Under commercially viable growth conditions, most CVD diamond crystals are brownish instead of near-colorless,”
Because of synthetic stones’ inherent color, “many manufacturers have started to treat the synthetic diamonds post-growth in order to transform unattractive brownish and yellowish stones into vivid colors,” says Hainschwang. The color of CVD and HPHT stones changes through irradiation, a type of radiation treatment, and annealing, a heat treatment that employs the HPHT process. Indeed, through these processes, most natural stones as well as synthetics can be altered to a desired color.
Companies like Suncrest Diamonds, based in Orem, Utah, use HPHT processing for just this purpose. “A lot of people will grow synthetics and want the color improved — so they’ll send them to us and we’ll run them at extreme temperatures in our high-pressure presses,” explains Sonny Pope, president of Suncrest Diamonds.
Due to ongoing advances in the HPHT process, stones can not only be transformed into many colors, but also improved as white diamonds. “The idea that we can improve whites by many grades is new — so that’s kind of exciting,” says Pope.
While treatments do make it more difficult to differentiate synthetics from natural stones, labs are not worried about their ability to accurately identify treated synthetics. “Multiple treatments do add a degree of complexity to the picture, but the characteristics of these gemstones are well documented in research literature, and this knowledge, in combination with our verification instruments, is sufficient to provide gemological laboratories with detection capability for these treated synthetics,” says Lawson.
While HPHT and CVD stones differ, “the detection methods employed are the same for both synthetic diamonds — each growth type requires only slight adaptations in the testing procedure,” notes Hainschwang. Synthetics can be identified as such by trained lab technicians who use the latest technologies to test for a synthetic stone’s unique characteristics, ranging from its chemical impurities to its crystal shapes.
“Methods involved in detection,” explains Hainschwang, “include microscopy, low-wave and short-wave ultraviolet testing, luminescence microscopy using various excitation bands, deep ultraviolet imaging, infrared spectroscopy, ultraviolet-visible and near infrared spectroscopy, energy dispersive x-ray fluorescence and last, but not least, photoluminescence spectroscopy.”
Given the different characteristics of HPHT and CVD stones, different detection methods work best for each. “While HPHT stones usually show some sectored growth zoning, typical inclusions or sectored luminescence, the CVD stones will unveil their identity after a photoluminescence spectrum has been performed,” says Hainschwang.
Labs that test for synthetics notice that, overall, the number of undisclosed synthetics they find is miniscule. “In most stones, we would estimate that the percentage of undeclared synthetics in the market is so small that it is quasi-zero,” says Hainschwang.
Given the inherent nature of synthetics and the processes by which such stones are manufactured, many believe that detection methods will continue to be the same in the future. As manufacturing processes become more sophisticated, “detection can become more challenging,” says Moses. “However, there are fundamental properties of synthetic diamonds — including growth patterns and spectroscopic characteristics — that are detectable by trained gemologists in a well-equipped laboratory. And we expect these distinctive features will continue to be present in laboratory-grown material because the growth processes used are so very different from natural diamond formation, which takes place over long periods of geologic time.”
RANDOM BATCH TESTING
Labs usually use these detection methods on random samples in submitted batches of melee stones. “It is not cost effective to send all melee to a grading laboratory, so currently a random testing approach needs to be taken, where a relatively small number of stones from each batch of melee is tested,” explains Lawson. “We are working hard to enable costs in this area to be reduced so that an affordable screening service for all melee stones can be offered by De Beers in the near future.”
While affordable screening for all melee stones is still a ways off, labs are making their screening services more accessible to diamond dealers. The GIA, for example, launched its Quality Assurance Service in the summer of 2012, which it advertises as a low-cost screening option. The service, which costs $12 a stone, tests random batches of loose and mounted diamonds, and is available for D to Z and fancy color diamonds of .20 carats and smaller and black diamonds of .50 carats and smaller.
SYNTHETICS IN THE MARKET
At first glance, the synthetic market might appear to be a serious threat to the natural diamond industry. According to a report commissioned by the Antwerp World Diamond Centre (AWDC) and prepared by New York business consulting group Bain & Company in 2011, entitled “The Global Diamond Industry: Lifting the Veil of Mystery,” about
5 billion carats of synthetic diamonds were manufactured in 2010. The overwhelming majority of these 5 billion carats, however, were used for industrial purposes. Indeed, less than .01 percent of the gem-quality diamond market was made up of synthetics in 2010, according to the report.
“The vast majority of our business is aimed at commercial purposes,” notes Joe Lancia, chief executive officer (CEO) of Scio Diamond Technology Corp., a synthetic diamond manufacturer in Greenville, South Carolina. Like all other synthetic producers, Scio,
which “started doing business in 2011 when it purchased assets from former synthetic manufacturer Apollo Diamond,” thinks of synthetic diamonds primarily as tools for industrial and technological advancements.
“Diamonds, after all, have the most versatile properties of any raw material on earth — whether it’s for optics, heat transformation or other tasks,” says Lancia. “Think of in the future using diamonds inside cell phones and laptops to reduce heat. They also can be used for medical equipment — on the surgical side, a diamond blade is the best precision tool available.” And while Scio “doesn’t have the capacity to be making enough carats to affect the natural diamond market, and is focused on the industrial-commercial side,” says Lancia, “we do have a small division that makes gem-quality stones.”
Almost all of the synthetics hitting the market are at least VS-quality stones. This is due more to the fact that manufacturers only put out high-quality stones that will be profitable than it is due to the control manufacturers have over their production. While there definitely is some level of control, “it’s imitating a natural process, so you are at the mercy of some natural forces,” explains Lancia. “We can grow up to 30 stones in one reactor, but we cannot predict that all 30 will be the same.”
The majority of the synthetics in the market are also priced at substantially lower price points than natural diamonds. “One of our laboratory-grown diamonds costs at least
25 percent less than a mined stone of the same size, cut and quality,” says Uzi Breier,
CEO of Washington D.C.–based CVD manufacturer Washington Diamonds, LP (WDLP), which started doing business in September 2012. Indeed, with price a key selling point, many manufacturers try to make their synthetics inexpensive to stay competitive in the market. “Currently,” adds Breier, “we are looking at distributors to offer our stones through the internet, providing the least expensive way to purchase beautiful diamonds.”
Aside from Scio Corporation and Washington Diamonds, there are only a handful of synthetic diamond manufacturers currently operating in the jewelry market worldwide. They include D. Nea Diamonds, Chatham Created Gems, LifeGem and Gemesis in the U.S., and New Age Diamonds in Russia. These manufacturers were unavailable for comment at press time.
IS THERE A THREAT?
While many in the diamond industry believe that improper disclosure of synthetic diamonds is a serious problem, given the small size of the synthetic market, they are confident in the industry’s ability to prevent it from becoming a real threat.
“The labs involved in identifying such misrepresentation should investigate the roots and disclose the names of the companies and owners where such material originated,” advises Nilesh Sheth, president of loose diamond manufacturer Nice Diamonds in New York City. “Trade members, once aware, will surely avoid working with these companies and their associates. And so far, there are only a couple of major producers of synthetic diamonds, so as long as they are compliant, this issue will be a one-time event and will not be a threat to the industry.”
As a precaution, from time to time, wholesalers send their stones to labs to test for synthetics. But most believe they are already insulated from any synthetic getting in their inventory through their established relations with trusted suppliers.
“I do certify some diamonds and I rely on these laboratories to detect the synthetic stones,” says Greg Telonis, president of Mr. Baguette, a manufacturer of small loose diamonds and jewelry in New York City. “But I do not use the laboratories regularly to check my inventory because I work directly with diamond cutters from Israel and Belgium and rely on them to sell me the proper product.”
“Overall,” adds Sheth, “we are comfortable in buying from vendors who are in business for a long time with good ethics and integrity — not from fly-by-night operators.”
The overwhelming opinion about synthetics is that, while they need to be properly separated from natural diamonds, they will always serve a particular niche in the market.
“I think everything has its place,” says Pope. “Natural diamonds will always be natural and rare. There have always been synthetics of every other gem and the natural gems don’t
“There is room for every product in the marketplace,” agrees Sheth. “Synthetics will also find their place in the market place, just as crystals, cubic zirconium and moisannite.”
The article is taken from http://www.diamonds.net/Magazine/Article.aspx?ArticleID=41268&RDRIssueID=96