COMINGS AND GOINGS Jerry Ehrenwald, who has headed the North American division of the International Gemological Institute since 1991, is leaving the lab to start the Laboratory Grown Diamond Exchange, a trading platform for created diamonds. He will be succeeded by Avi Levy, a veteran of diamond companies Star Diamond, MJJ Brilliant, and Renaissance Jewelry. Forevermark has let go six employees at its U.S. division, including two employees who had long been the face of the De Beers–owned brand: vice president of sales Kevin Lane and vice president of partner development and training Jeffrey Skaret. A company source said the brand is not downsizing but changing direction. The Diamond Development Initiative (DDI