The prices can be just half the cost of a similar ring at a big-box jewelry store. Compared to online jewelers, here's the general observation: Diamonds 1 carat and above have similar pricing, since the diamonds are certified by GIA. Diamonds under 1 carat are cheaper at Costco, since they're not certified.

Each piece of jewelry is thoroughly scrutinized for diamond quality, as well as overall manufacturing and craftsmanship. Costco's team of Gemologists, all of whom have graduated from a GIA program, inspect for diamond color, clarity, cut, and carat weight.

As part of Signet Jewelers, the world's largest diamond retailer, Zales has a responsibility to not only set a good example of providing responsibly sourced natural diamonds but also to be a leader in developing standards that make responsible sourcing the norm.