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.

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.

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.

The industry had been one of the great winners of the global pandemic, as stuck-at-home shoppers turned to diamond jewelery and other luxury purchases. But as economies opened up, demand quickly cooled, leaving many in the trade holding too much stock that they'd bought for too much money.