The recycled diamonds trade has become a huge, under-the-radar market. But how is it affecting the industry—and consumers who may get lowballed?In an oft-cited, frequently recycled 1982 Atlantic article, Edward Jay Epstein spoke of his troubles trying to unload a diamond on 47th Street. “Retail jewelers,” he declared, “prefer not to buy back diamonds from customers, because the offer they would make would most likely be considered ridiculously low.”Four decades later, he’d have far less of a problem. The gold-buying boom kept many retailers afloat during the recession. But now that the price of gold has fallen and trade-in fever has cooled, it doesn’t take much for jewelers to add “and diamonds” to those “we buy gold” signs.The result is a massive market for secondhand diamonds that has largely operated under the radar. There are now thousands of places for consumer