The owner of Zales and Kay Jewelers will no longer buy diamonds and other precious gems originating in Russia – a surprise reversal that comes as companies around the world cut ties in response to the invasion of Ukraine.

Signet Jewelers cited the mounting sanctions targeting Russia and its business entities in a memo to suppliers explaining the decision. The company’s decision to halt purchases from Russia could have major implications for the global diamond trade.

Russia is the world’s largest source of precious gems and the world’s largest diamond producer by volume. Russia’s Alrosa PJSC is partially owned by The Kremlin.

“Signet has therefore halted all trade in precious metals and diamonds that originate from such sanctioned Russian sources, and you are therefore requested to stop supplying the same to Signet even though the country(s) in which you operate may not have imposed sanctions on Russian precious metals and diamonds,” Signet said in the memo, according to Bloomberg.

The block on Russian gems will complicate matters for suppliers, since diamonds sourced from other countries are often mixed together during production in hubs such as Antwerp and Dubai, Bloomberg reported. The US accounts for roughly half of the world’s diamond sales.

Signet’s memo noted the directive only applies to gems that were purchased after Feb. 24 – the day that Russian troops rolled across the border to invade Ukraine. That means it could be several months before the diamond industry experiences a supply crunch.

Earlier this month, President Biden issued an executive order banning imports of Russian “luxury items,” including “nonindustrial,” or rough diamonds. In other words, the order does not impact diamonds that are cut or shaped in other countries and then shipped to the US.

While discussing the block during an earnings call, Signet CEO Gina Drosos said Russian-made diamonds were a “very small impact for us” – noting the company wanted to make sure its products were ethically sourced.

“We’ve been an industry leader in responsible and ethical sourcing now for more than a decade,” Drosos added.

In a quarterly earnings release on Thursday, Signet noted it has “suspended business interaction with Russian-owned entities since the beginning of the invasion, in unity with all those in the world calling for peace.”

Signet added that it “does not contemplate a material impact relating to the Russian invasion of Ukraine” in the upcoming fiscal year.