LONDON  - Commodity prices saw mixed fortunes this week as traders tracked concerns over the world economic outlook driven by fresh debt tensions in the eurozone, most notably Spain.

“Commodity prices have posted widespread and broad-based price weakness over the week,” said Barclays Capital analyst Sudakshina Unnikrishnan.

“The re-emergence of China and US growth concerns, plus worries over Spanish sovereign debt, are undermining commodity prices. “We recommend being alert to buying opportunities in the weeks ahead, especially in base and precious metals.” Investors meanwhile drew some comfort from successful Spanish bond auctions that partly soothed concerns over the eurozone debt crisis.

OIL: World oil prices were mixed, with traders torn between global economic growth concerns and simmering tensions over key crude producer Iran. The market rose on Tuesday after a successful Spanish bond auction, encouraging US corporate earnings and the higher global growth forecasts from the International Monetary Fund. Prices were also supported by renewed concerns over the standoff between key producer Iran and the West over Tehran’s nuclear programme.

However, prices then tumbled on Wednesday after figures showed a much larger-than-expected increase in American crude inventories, indicating weak demand in top global consumer the United States.

US crude stocks jumped by 3.9 million barrels last week, more than four times the expected gain of 900,000 barrels.

The market clawed back some ground on Friday, supported by rising European stock markets and a weaker dollar as investors drew comfort from a successful longer-term Spanish bond auction and rising German business confidence.

The weaker US unit makes dollar-priced crude cheaper for buyers using stronger currencies and this tends to stimulate demand and push oil higher.

Spain—one of the eurozone’s debt-strapped economies—paid a higher borrowing rate in a key auction of 10-year bonds on Thursday but managed to keep it below the psychologically key six percent level. Rates above 6.0 percent are generally perceived to be unsustainable over the longer term.

Elsewhere, credit agency firm Fitch Ratings warned that oil prices could pressure sovereign ratings of major economies and firms if they see a further spike.

“The biggest risk to ratings is of a shock oil price rise that leads to sustained higher prices,” it said in a commentary.

“The US economy would be damaged in the short and medium terms if oil prices were to remain higher than $150 per barrel.” By late Friday on London’s Intercontinental Exchange, Brent North Sea crude for delivery in June dropped to $119.21 a barrel, compared with $121.28 for the May contract the previous week. On the New York Mercantile Exchange, West Texas Intermediate or light sweet crude for May rose to $103.88 from $103.01.

PRECIOUS METALS: Most prices lost ground as traders worried about the global outlook and falling stocks.

“Gold is currently behaving more like a risky asset class and less like a safe haven,” said Commezbank analysts.

“However, the price is likely to regain its former peaks by the end of 2012 as a result of its return to a store of value, low interest rates and the appetite for gold in China.”

By late Friday on the London Bullion Market, gold slipped to $1,641.50 an ounce from $1,666.50 the previous week.

Silver dropped to $31.79 an ounce from $32.36.

On the London Platinum and Palladium Market, platinum retreated to $1,579 an ounce from $1,600. Palladium advanced to $666 an ounce from $643.

BASE METALS: Prices sank to their lowest levels since early January, before ending on a mixed note. “The rollercoaster ride on the metal markets continues, though the overriding trend would appear to be downwards,” Commerzbank analysts said in a research note.

A slew of weak economic data from the United States weighed on financial markets.

US Labour Department figures released on Thursday showed initial jobless claims fall by 2,000 to 386,000 in the week ended April 14, far short of the 375,000 expected by analysts, raising concerns over the recovery of the country’s beleaguered labour market.

Existing home sales also fell by 2.6 percent in March from February, the US National Association of Realtors said.

By late Friday on the London Metal Exchange, copper for delivery in three months rose to $8,181 a tonne from $8,040 the previous week. Three-month aluminium firmed to $2,081 a tonne from $2,078.

Three-month lead rose to $2,117 a tonne from $2,062.

Three-month tin fell to $21,650 a tonne from $22,525.

Three-month nickel sank to $17,858 a tonne from $18,400.

Three-month zinc climbed to $2,024 a tonne from $2,008.

COCOA: Cocoa futures were mixed as traders paused for breath following last week’s strong rally.

By Friday on LIFFE, London’s futures exchange, cocoa for delivery in July eased to £1,452 a tonne from £1,454 the previous week. In New York on the NYBOT-ICE, cocoa for July stood at $2,221 a tonne compared with $2,188.

COFFEE: Coffee also witnessed diverging prices.

By Friday on NYBOT-ICE, Arabica for July fell to 177.30 US cents a pound from 182.10 cents for the May contract the previous week.

On LIFFE, Robusta for delivery in July advanced at $2,031 a tonne compared with $1,995.

SUGAR: Sugar futures hit their lowest point since May 2011 as traders eyed the prospect of plentiful supplies from Brazil.

By Friday on LIFFE, the price of a tonne of white sugar for delivery in August retreated to $582.90 from $622.20 the previous week.

On NYBOT-ICE, the price of unrefined sugar for May dropped to 21.67 US cents a pound from 24.11 cents.

GRAINS AND SOYA: Prices declined across the board.

By Friday on the Chicago Board of Trade, maize for delivery in May fell to $6.16 a bushel from $6.29 the previous week.

Wheat for May dropped to $6.19 a bushel from $6.23.

July-dated soyabean meal—used in animal feed—dipped to $14.26 a bushel from $14.40.