Costco is selling platinum bars as it expands its precious-metals business after huge success selling gold

• Costco is selling 1-ounce platinum bars online for $1,090.
• The move comes about a year after the retail giant started selling gold bars and silver coins.
• Platinum prices are stable year to date but have risen 14% over the past year.

Costco is diversifying its precious-metals business by selling 1-ounce bars of platinum for $1,090.

The retailer is selling the item online, according to a web listing.

According to the listing, the item, which is available only to Costco members, is 999.5 pure platinum and Swiss-made. The bar features an image of Lady Fortuna, the goddess of chance, luck, and fate.

While the price of platinum is about flat year to date, it's up 14% over the past year, with futures trading Thursday at about $1,000 an ounce.

Costco sales of the 1-ounce platinum bar appear to have begun sometime in the past two months, with the product already racking up 14 five-star reviews from verified purchasers.

"Great addition to any precious medals collector," one buyer said in their review. "I have purchased gold coin and bars, this is 1st I spotted the platinum bar on here. It seemed to be fair priced and good deal with the cash rewards back!"

Costco imposes a limit of one transaction per membership, with a maximum purchase of five bars.

The sale of platinum bars comes about a year after Costco started selling gold bars and silver coins, and it's grown into a big business for the company, as it typically sells out of its gold inventory in just a few hours once the product goes online.

"I've gotten a couple of calls that people have seen online that we've been selling gold — 1-ounce gold bars," Costco CFO Richard Galanti said in an earnings call last year. "Yes, but when we load them on the site, they're typically gone within a few hours, and we limit two per member."

Costco's gold and silver sales have surged to $200 million a month, Business Insider previously reported.

While the company is selling a lot of precious metals, it's probably not making much of a profit from them, which is not unique to its operating model of relying on its membership fees for profits.

"Pricing at that level and shipping costs suggests it's a very low profit business at best," Edward Kelly, a Wells Fargo retail analyst, said earlier this year.