Gems of war: scientists struggle to identify conflict diamonds.
The diamonds that buy the arms and supplies in such conflicts are almost entirely from Liberia, Sierra Leone, The Democratic Republic of the Congo, and Angola. All are nations blessed with vast mineral wealth but suffering from ongoing attempts to overthrow their internationally recognized governments. The United Nations has a name for such gems: conflict diamonds.
Rough diamonds are usually smuggled from these areas to more peaceful, neighboring states and there enter the international market. The profits go back to the often terrorism-bent rebels. A Dec. 30, 2001, article in the Washington Post linked some trade in conflict diamonds in Congo to the terrorist groups Al Qaeda and Hezbollah.
The problem of conflict diamonds is huge. According to Global Witness, a London-based advocacy organization, an Angolan rebel army known as Unita generated $3.7 billion over 6 years in the 1990s largely through trading these gems. Global Witness estimates that total world-diamond production in 1999 was worth $6.8 billion.
Conflict diamonds make up about 2.5 percent of annual worldwide production, says Jeffrey Harris, an earth scientist at the University of Glasgow in Scotland and a scientific consultant to the giant South African diamond conglomerate De Beers. Other scientists give estimates of up to 4 percent.
U.N. sanctions and humanitarian organizations' efforts to keep conflict diamonds off the market haven't been effective. The gems smuggled out of suspect areas are usually indistinguishable from legitimate diamonds. Variations that are easily visible can turn up within a single mine. Only in rare cases do unusual characteristics, such as a particular yellow tint, characterize a site. Compared with other types of gems, high-quality diamonds are remarkably similar between sites, a problem that's exacerbated when stones are polished.
Could science hold the key to stamping out this deadly trade? Some geoscientists argue that chemistry and physics can identify conflict diamonds. Like a fingerprint, unique characteristics such as composition or microscopic structural imperfections could indicate where a diamond originates, they say. Diamonds entering the market could be tested to determine their origin, and gems found to come from conflict zones under U.N. sanctions could be confiscated.
Work to forensically identify diamonds has grown out of research into diamond formation and other geological processes within Earth.
Geologists and mineralogists have always had an interest in how diamonds form, says Steven E. Haggerty of the University of Massachusetts in Amherst. He points out that much of what we know about conditions in Earth's mantle has come from studying the gems, which form at depths down to 2,800 kilometers and can be as much as 3 billion years old. However, "the field really has now taken on a very different significance," says Haggerty.
In May, scientists attending a Washington, D.C., meeting of the American Geophysical Union (AGU) discussed several possible methods for fingerprinting diamonds. Virtually all efforts to determine the origin of diamonds look for chemical variations in the gems, though many of those efforts have proved fruitless, says Peter J. Heaney of Pennsylvania State University in State College.
Alternatives include detecting radiation damage invisible to the naked eye and characterizing proportions of tiny embedded impurities. Some scientists attending the meeting were encouraged by the new proposals, but others maintained that diamonds are remarkably difficult to identify and a practical scientific method for culling conflict diamonds is a distant dream.
MISSION IMPOSSIBLE The idea of forensically identifying conflict diamonds came to many scientists' attention at a White House conference shortly before President Clinton left office in 2001. "To be honest, I was only modestly aware of conflict diamonds before this," says Edward Vicenzi at the Smithsonian Institution's National Museum of Natural History in Washington, D.C. Before the Clinton administration departed, it wanted to steer some research funding to the issue, says Vicenzi.
At that conference, he says, diplomats and commercial-diamond experts were asking scientists how to identify the origin of diamonds. The scientists' response was that no feasible method exists.
The uniformity of gem-quality diamonds is part of the problem. Many other gems have relatively complex structures. Emeralds, for example, which are composed of beryllium aluminum silicate with a dash of chromium, are generated by a variety of geological recipes. Small differences in impurities and chemical makeup of these green gemstones readily betray their origin (SN: 3/11/00, p. 175).
Diamonds, in contrast, are relatively pure, and all are created under similar conditions. Identifiable impurities crop up in parts per million, per billion, or even smaller concentrations, making it next to impossible to distinguish among the gems' geographic sources, says Heaney. The more valuable the diamond is, the harder it is to identify.
"Consumers want diamonds to be pure with no ... imperfections," he notes, but these are exactly the characteristics that might help mineralogists determine the gems' origin.
Scientists haven't let this paradox dissuade them from searching for other types of diamond fingerprints. Since diamonds are almost entirely carbon, some attempts to fingerprint them have examined ratios of different types of carbon atoms, or isotopes. Carbon atoms typically have six protons and six neutrons, but isotopes occasionally crop up that have seven neutrons. Therefore, some scientists have postulated that diamonds from a particular location might have a characteristic ratio of the two types of carbon isotopes. Unfortunately, says Heaney, "in reality, there is very little trend in isotope ratios" from one diamond-mining region to another.
Researchers are also looking at nitrogen, the most common impurity in diamonds. This element is structurally similar to carbon and sometimes slips into a diamond's structure. Again, says Heaney, there appears to be little pattern in nitrogen abundance between mining regions.
A different method looks not to the diamond structure but to tiny mineral grains, known as inclusions, that get trapped within the diamond as it grows. James Farquhar of the University of Maryland in College Park and his colleagues announced at the recent AGU meeting that diamonds formed during different geological periods have variable abundances of rare sulfur isotopes within these inclusions. The scientists managed to find specific sulfur-isotope ratios common to eight diamonds known to be from a single mine in Botswana yet not to the other diamonds tested. The researchers, however, have yet to apply the technique to diamonds from any conflict zone.
ROCKY RARITY Heaney and Vicenzi both work with rare diamonds known as carbonados, which are found only in Brazil and central Africa. Carbonados aren't of gem quality. Unlike their more valuable brethren, each stone consists of multiple crystals, is black or gray, and has many imperfections. Techniques that reveal these imperfections may eventually be applicable to more costly diamonds.
Imperfections in carbonados manifest themselves as missing carbon atoms or entire missing layers in a crystal structure. New methods show that these same characteristics sometimes turn up in ordinary diamonds. The defects may be the key to tying any diamond to its source, says Heaney.
At the AGU meeting, Heaney discussed his work comparing defects in carbonados acquired from two sources. His team used a high-energy beam of gallium ions to shear thin slices from stones and then examined the slices under a powerful electron microscope. The frequency of types of defects differed between samples from the two sources.
Most researchers are attempting to find a single method that would identify diamonds from anywhere, says Vicenzi. However, since this seems beyond researchers' grasp at the moment, "we have to come up with alternatives," he says. Finding specific, rare characteristics that tie diamonds to specific sources may provide a partial solution until a more universal method is developed.
Vicenzi reports one type of rare characteristic that appears in some carbonados. Deep within Earth, some diamonds come into contact with radioactive materials, such as thorium or uranium, that can impart a unique signature known as a radiation halo.
To detect this rare damage, Vicenzi and his colleagues bombard the surface of a diamond with electrons, which cause it to throw off a pattern of light influenced by the radiation damage. The areas of damage produce a bull's-eye of light that appears to be consistent among stones to similar types and intensities of radiation.
The team has used this technique to characterize carbonados from the Central African Republic. Although it hasn't yet been tried on gem-grade stones, Vicenzi holds that this technique could be adapted to flag contraband gems from specific regions.
There are some inherent problems with any technique that depends on a single characteristic to link a gem to its source, says geologist Eva Anckar of the University of Cape Town in South Africa. "Any one, single characteristic does not sufficiently discriminate between diamonds from different sources," she says. Also, many methods being tested require partial destruction of the gem. Instead, her team proposes a method that takes into account several variables and leaves gems whole.
The scientists first shine an infrared beam through intact diamonds and measure the wavelengths absorbed. These data reveal impurities, such as nitrogen, hydrogen, and oxygen locked within the diamond, Anckar says. The researchers then combine these data with various measurements of the color and overall shape of rough diamonds.
In a pilot study, the scientists compiled eight measurements on each of 495 diamond specimens that came from three mines. Using multiple characteristics and complex statistical methods, the researchers found that diamonds from each site--two in South Africa and one in Canada--showed unique clusters of characteristics.
"The method shows great promise," says Anckar, though it requires examining whole parcels of gems from any given region, because it's the range of characteristics over a group of gems that gives away the identity.
Anckar is currently compiling those profiles for diamonds in a "global atlas of diamond characteristics," she says.
PIPE DREAM "Strictly analytical methods all suffer from critical weaknesses," says Harris. Practicality is the biggest drawback of stone-by-stone analyses, he says. He has calculated that most methods would be so time consuming as to be impractical. Moreover, complex analytical techniques that require slicing gems will probably never be implemented, Harris says.
Another flaw in proposed gem-tracing plans, he continues, is that no one has a comprehensive reference collection of diamonds from conflict areas, a problem made more difficult by the fact that collecting such gems is illegal.
James E. Shigley of the Gemological Institute of America in Carlsbad, Calif., takes a similar view of the difficulties of identifying diamonds. "Every year, several tens of millions of diamonds are mined and turned into hundreds of millions of [jewels]," he says. Identifying all these stones would be a "daunting challenge" he notes.
"We also have to think about protecting ... legitimate business," says Shigley. "Many countries such as Botswana and Namibia rely heavily on this revenue."
Shigley holds a more basic reservation about the possibility of identifying diamonds by their origins. "Diamonds don't come from conflict countries, they come from the center of the Earth," he says. Consequently, they're more likely to reflect conditions in Earth's mantle than any that define political boundaries.
Furthermore, he says, many of the characteristics of rough diamonds, such as overall shape, surface markings, and some mineral inclusions, are systematically removed during cutting and polishing. This makes identification of jewels even more difficult than that of the rough diamonds that researchers have used in their analyses.
International groups and the large diamond producers aren't waiting for science to succeed. They've created a new diamond-certification program that won't require detailed analysis of the stones. Beginning this November, it will track legitimate diamonds all the way from the mines to consumers. In accordance with the so-called Kimberley process, diamonds will be catalogued and assigned a certificate as soon as they are dug up. These certificates will then be required at every step as the gems move from the mine to wholesale dealers, cutters, polishers, retail sellers, and eventually consumers. In the absence of practical analytical techniques, "the certification program should move forward and can be complemented by the scientific program," says Harris.
Other scientists are less convinced that the Kimberley process will work. "It's outrageously naive to suggest the [certification program] will solve the problem," says Haggerty. "If people can successfully duplicate and modify passports, driving licenses, and banknotes, they won't have any problem at all duplicating so-called certificates of authenticity," he says.
Heaney and Vicenzi also have reservations the certification program. Instead, the two researchers are promoting the creation of a database of mine-by-mine diamond characteristics and a reference collection of diamonds, both to be held in the United States. To get diamonds for this purpose from conflict zones will require special dispensation from organizations such as the United Nations, they say.
Though Heaney says it may be a decade or more before a practical method for fingerprinting diamonds will be developed, he's optimistic the problem will be solved.
"Reality should not necessarily get in the way," says Haggerty. "Just because we don't know of a method to characterize a diamond geographically doesn't mean that no method exists," he says. "We are still hell-bent on understanding the formation of diamonds, [and now] we have a moral obligation to solve this."
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|Date:||Aug 10, 2002|
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