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Signet Jewelers is the largest diamond retailer globally.

Shares of Signet Jewelers Ltd. (SIG - Get Report) lost their sparkle Thursday, Jan. 17, after the retailer cut its fourth-quarter and fiscal 2019 guidance amid slower-than-anticipated holiday sales.

Signet shares fell 24.7% to $25.13 at the close of trading on Thursday on the New York Stock Exchange. 

The Akron, Ohio-based retailer said in a statement that it now expects fourth-quarter same-store sales to fall 1.6% to 2.5%, with adjusted per-share earnings of between $3.77 and $3.92, including a 19-cent charge for a previously disclosed regulatory matter.

Analysts polled by FactSet had been expecting fourth-quarter adjusted earnings per share of $4.08. 

For the full year, Signet said it now expects same-store sales to be flat vs. prior guidance of flat to up 1% and adjusted per-share earnings in the range of $3.53 to $3.68, vs. its prior guidance of $4.15 to $4.40 on sales of $6.26 billion, down from previous expectations of $6.31 billion.

Analysts polled by FactSet had been anticipating full-year per-share earnings of $4.25 on sales of $6.29 billion.

"Early improvements in refreshed merchandise assortment, digital marketing and OmniChannel were more than offset by larger-than-expected declines in legacy product lines," CEO Virginia Drosos said in a statement.

"In addition, the competitive promotional environment we saw early in the season intensified in December and, despite our increased promotional investments, we experienced reduced traffic during key December gifting weeks," Drosos said.