The China ex-works Shanxi daily spot alumina assessment stood at Yuan 2,540/mt ($381/mt) cash on Thursday, firming another Yuan 40/mt, after gaining Yuan 30/mt on Wednesday.

The current price also reflected an increase of Yuan 70/mt on the week, and was up Yuan 20/mt from last month.

The bid-ask spread stood at Yuan 2,530-2,550/mt cash on Thursday.

Market sentiment has strengthened mainly on the back of potential bauxite mine shutdowns in Shanxi, Chalco floating a 90,000 mt spot buy tender, higher domestic aluminum prices, and Shanxi refiner Luneng Jinbei cutting back partial refinery run rate in August.

"We're hearing offers at a minimum of Yuan 2,550/mt cash now. We won't pay that level yet as we have enough term supply for now, and the market is too volatile. But those really desperate to buy will have to pay," a Sichuan smelter said.

"Most sellers are holding back offers now, expecting higher prices. They have stock, but just not selling. Refiners are eying up to Yuan 2,600/mt in the near term," a Shanxi refiner said.

In the near term, spot alumina prices are likely to continue testing higher, as metal prices stay strong and anticipated upcoming winter refinery cuts continue to support the market, sources said.

"There's a strong speculative atmosphere now, especially in futures trading," a trader added.

On Thursday, the front-month aluminum contract on the Shanghai Futures Exchange closed at Yuan 16,420/mt Thursday, up from Yuan 15,900/mt a week ago, and also from Yuan 14,330/mt last month.