Costco may not be the first store that comes to mind when you think about shopping for a diamond ring. But the sparkly jewelry case often positioned near the wholesale club store entrance is enough to make many shoppers curious about the wisdom of buying fine jewelry there.

Here are some things you should know before you buy a diamond ring from Costco or anywhere else.

Understanding the 4Cs

Most jewelry retailers use the Gemological Institute of America (GIA) color, clarity, cut, and carat weight standards, also known as the 4Cs, to set stones’ prices. The rating for these characteristics determines the quality of a diamond. The cut is a matter of personal taste, but the quality of the cut matters to its brilliance.

Clarity is a measure of the stone’s purity, with designations like VVS1, or very, very slightly included, and VS1, for very slightly included. Color is rated on a scale of D to Z, with D being the best, or colorless, quality.

Costco guarantees that the diamonds it sells are at least VS2 in clarity and grade I in color. Its diamond rings with a center stone that is 1.00-carat or larger come with a GIA Diamond Grading Report. Diamonds over one carat come with an International Gemological Institute (IGI) appraisal that can be used to ensure the fine jewelry investment.

Tiffany offers consultations during the shopping process with diamond experts in-store, by phone, or by email.

Diamond Price Ranges

A one-carat or more diamond ring can sell for anywhere between $3,500 and $40,000, depending on those 4Cs, the setting’s quality, and the retailer.

As of August 2022, the Costco website lists rings starting at $479.99 for a simple stackable band in 14k gold with a 0.25-carat VS2 diamond. The priciest offering at this writing is a $349,999.99 ring set in platinum with a 1.54-carat pink diamond rated with VVS1 clarity.

For comparison, a solitaire diamond ring at Tiffany’s starts at $14,000, with many customizable options for size, color, and setting. Many of the rings displayed on its website are embellished with diamonds, often clustered with other stones.

Online diamond retailer Blue Nile Inc. sells loose diamonds and pre-set diamond rings and lists one-carat stones starting at about $1,340. Blue Nile shoppers can choose from several setting styles for the diamond that they select at an additional cost. It uses the GIA rating system.

Customization and Service

Old-fashioned jewelry stores allow customers to customize their purchases. If you like a stone in one ring but the setting of another, many jewelers will make a custom version for you. Some even allow you to design your own ring and will work with you to produce a one-of-a-kind ring based on your description.

When you purchase a ring from a traditional jeweler, you can generally take it back when it needs cleaning or repairs or even have a gemstone reset in a new piece of jewelry.

All Costco diamond rings are pre-made, and buyers don’t have the option to customize them. The specifications on the Costco website list ring sizes, but you will have to take your ring to a jeweler if you need to have it sized to fit.

Costco does not offer cleaning or repairs for its jewelry.

Tiffany vs. Costco

In August 2017, a federal judge ruled Costco owed Tiffany at least $19.4 million in damages, lost sales, and interest for selling rings falsely advertised as Tiffany jewelry. The trial followed a 2015 verdict against Costco in the U.S. District Court in Manhattan. A jury determined the company was guilty of trademark infringement for using Tiffany to describe rings in its jewelry cases. Costco had argued that Tiffany was a generic term used to describe a style of ring setting.

If nothing else, that notorious case suggests that a consumer considering fine jewelry should know the basics before buying fine jewelry.