NEW YORK, United States — Tiffany & Co. is suffering from currency fluctuations and a jittery global economy, but there's one definite bright spot for the luxury jeweller: lower diamond prices.

The cost of commodities like gems and metals is declining, which will help bolster gross margins, the New York-based company said on a conference call Friday. Lower metal expenses have already driven an improvement in profitability, and the benefits from cheaper diamonds will show up in results next year, Tiffany said.

The shift could add 3 percentage points to margins, bringing a multiyear tailwind to the jeweler, according to Jefferies analyst Randal Konik. That’s helping the company cope with challenges on several fronts. Tourism spending is down, the strong U.S. dollar is crimping sales, and demand for luxury goods overseas has been sluggish.

Comparable sales — a closely watched measure — fell 5 percent globally in the fourth quarter, excluding currency fluctuations. That was close to the 5.1 percent drop that analysts expected, according to the average of estimates compiled by Consensus Metrix.

Earnings, meanwhile, exceeded estimates. They amounted to $1.46 a share, excluding some items. Analysts had projected $1.40 for the period, which ended Jan. 31.

Tiffany shares climbed as high as 4 percent to $72.90 in New York on Friday. The stock had been down 8.1 percent this year through Thursday’s close.

By Nick Turner and Lindsey Rupp: editors: Nick Turner and Kevin Orland.