METALS-Profit-taking, onset of long holiday in China weigh on copper

By Polina Devitt

LONDON, Sept 30 (Reuters) - Copper slipped on Tuesday as the onset of a week-long holiday in top metals consumer China coincided with the end of the third quarter, prompting profit-taking after prices hit their 15-month high last week.

Benchmark three-month copper CMCU3 on the London Metal Exchange fell 1.4% to $10,275.50 a metric ton by 1600 GMT.

The metal, used in power and construction, is on track to close the third quarter with 4% growth as many analysts lowered their 2025 and 2026 market supply estimates after this month's disruption at the Grasberg mine in Indonesia.

The prospect of lower supply from Grasberg led copper to hit a 15-month high of $10,485 on Thursday and reduced the discount of the LME cash prices against the three-month copper contract CMCU0-3 to $28 a ton from $73 a week ago.

In China, the Yangshan copper premium SMM-CUYP-CN, which reflects demand for copper imports, fell 6% to $50 a ton, a six-week low, ahead of the October 1-8 National Day holidays, when trading activity is low.

Data showing China's manufacturing activity shrank for a sixth month in September further dampened market sentiment.

"Looming U.S. government shutdown is another factor making the market a bit nervous," said Dan Smith, managing director of Commodity Market Analytics. A government closure would delay the release of Friday's key employment numbers.

Among other LME metals, tin CMSN3 lost 0.4% to $35,260 a ton as the Indonesia Tin Exporters Association said a crackdown on illegal mining activities on tin hub Bangka Island would not disrupt shipments from the region.

With this order, tin hit $35,510, its highest since April 4, on Monday. The association expects Indonesia's refined tin exports to rise 18% to 53,000 tons this year.

Lead CMPB3 lost 0.3% to $1,988.50. Data showed on Tuesday that lead inventories in warehouses monitored by the Shanghai Futures Exchange fell 15% from Friday to their lowest level since February.

LME aluminium CMAL3 fell 0.1% to $2,677 a ton, zinc CMZN3 added 0.2% to $2,945.50, and nickel CMNI3 lost 0.6% to $15,220.