"Most people who are buying over the Internet have done their homework. They are comfortable, they are a little computer savvy, they know what color is, they know what cut is, and all you need to do is start comparing sizes and qualities with other like sizes and qualities," Johnson said.

The bottom line is that there are deals to be had online. Here are some guidelines for savvy shoppers:

• If you decide to go shopping online, check the site's reputation. It should be a member of Jewelers of America or the American Gem Society.
• Shop on a site that offers reports from accredited labels like the International Gemological Institute or the Gemological Institute of America.
• Make sure the site has a toll-free phone number so you can talk to a real person if there's an issue.
• Make sure any resizing and shipping is free.
• Look for an online jeweler with a 30-day return policy -- no questions asked.