GIA Finds Clues to Continent Formation

RAPAPORT... Mineral inclusions in rare diamonds have provided clues towhen their continents of origin were formed, according to research by the GemologicalInstitute of America (GIA). The researchers studied sulphide inclusions in type Ibyellow diamonds originating from the Zimmi mining area near the Liberia-SierraLeone border. Those stones have rare nitrogen impurities, and comprise less than0.1% of the world's natural mined diamonds, the GIA noted. "Diamonds are one of the most valuable gems, not only asjewelry, but also in geoscience," said GIA research scientist Karen Smit. "Themineral inclusions in diamonds let us study the inaccessible depths of Earth -somewhere that today's science cannot otherwise reach." The group, led by Smit, laser-cut and polished very thinplates taken from the Zimmi diamonds, and were able to isolate and study thesulphide they contained. They then extracted chemical isotopes that providedinformation on the deepest and oldest parts of the continent in which they were found. "This kind of insight is possible only because of the unique characteristics of diamonds," said Dr. Wuyi Wang, vice president of research and development for the GIA. The GIA conducted the study together with researchers from the Washington-headquartered Carnegie Institution for Science, and the University of Alberta. The results were published in Science magazine. Image: A rough Zimmi diamond with a sulphide inclusion (above); a close-up view of the inclusion inside the diamond (below). (GIA)