Copper futures spike in freak move that Wall Street can't quite explain

  • Analysts couldn't point to a specific headline behind a more than 2.5 percent jump in copper prices Monday morning
  • Thousands of workers at Freeport-McMoRan's Grasberg mine in Indonesia staged a rally Monday ahead of a planned month-long strike that could constrict supply.
  • Key copper-trading markets in London and Shanghai were closed Monday for a holiday.
An employee scans barcodes on copper rods
Krisztian Bocsi | Bloomberg | Getty Images

Copper prices suddenly surged to a near one-month high Monday morning, but several on Wall Street were uncertain about exactly what caused the spike.

Copper futures for July delivery briefly leaped more than 2.5 percent around 9:31 a.m. EDT, hitting $2.6945 a pound, their highest since April 5. Copper traded about 2.3 percent higher as of 10:45 a.m.

It was the kind of move that typically comes when a single big piece of news hits, but traders were scratching their heads.

Copper intraday performance Monday

"I can't see any [headline] in particular," said Dane Davis, commodities research analyst at Barclays. He noted that a strike was set to begin Monday at Freeport-McMoRan's Grasberg mine in Indonesia and a weaker U.S. dollar supported copper's move higher.

Thousands of workers at the world's second-largest copper mine staged a rally on Monday ahead of a planned monthlong strike to protest layoffs, a union leader said in a Reuters report.

The U.S. dollar index traded slightly lower on the day.

Low trade volume was also a likely factor behind the commodity's jump. Key copper trading markets in London and Shanghai were closed Monday for a holiday.

Eric Hunsader, founder of Nanex, first pointed out the move in a Tweet:

"The fact that it stayed high tells me something's happening, there's some news," he told CNBC. "This is sudden."

Copper rose 2.76 percent last week ahead of Monday's spike.

— Reuters contributed to this report.