Hardly anyone podcasts about jewelry. Here’s why retailers should see streaming audio as an opportunity. Diamonds and gemstones may be rare, but podcasts covering those subjects are even rarer. Look on iTunes for podcasts that cover technology and you’ll find hundreds. But hunt for jewelry-related podcasts and you’ll come across only a handful. Podcasting has exploded in recent years: According to Edison Research, one in five Americans listened to a podcast in the last month, up from 9 percent in 2008. And most experts see it getting bigger. Podcasts are audio (and sometimes video) shows that can be downloaded from or streamed over the Internet. The name, which combines the words iPod and broadcast, was coined in 2004. “People are consuming content differently,” says Rod Worley, founder of FourGrainer.com and host of the Inside the Jewelry Trade podcast. “We all want it q