The industry has had an up-and-down-though mostly down-relationship with Rep. Tony Hall (D-Ohio), the congressman whose CARAT Act calls for every diamond to be sold with a "certificate of origin." But now some hope the industry finally has a good working relationship with the mercurial human rights activist. In October, Hall, accompanied by young victims of Sierra Leone rebels, spoke at a "conflict diamond" demonstration in front of Cartier in New York. Hall says he was motivated by the industry's campaign against his second version of the CARAT Act-especially a letter sent by Jewelers of America to its members asking them to oppose the bill. (The second act still calls for certification of polished diamonds, although this would be waived if the industry set up a rough certification system.) Hall was also upset that someone in the industry-not JA-had gone to the House Republican lead