...[With] up to 90 percent of the world's rubies and many other precious gems mined in Myanmar, chances are that a vast proportion of the stones glinting in the windows of high-end jewelers worldwide originate in the military-ruled nation...But human rights groups and some dealers are urging a boycott, and compare the gems with Africa's so-called blood diamonds, which are mined in war zones to finance further violence... However, some gem dealers and experts dismiss attempts to boycott Myanmar's precious stones as futile and unnecessary... "The stones will go to the black market, it is no different, because of the demand in the market," says Pornchai Chuenchomlada, president of the Thai Gem and Jewelry Traders Association (TGJTA)... "The fact that virtually every Burmese-origin gemstone offers benefit to one of the most oppressive regimes on the planet made our decision to boycott Burmese gemstones very clear," Brian Leber, a jeweler, tells AFP... One of the highest-profile companies boycotting Myanmar's gems is Tiffany & Co... But Leber says there are still plenty of jewelers who are either ignorant of the situation or turn a blind eye.