The strike entered its fifth day on Monday, as the union awaited a decision by labor authorities over whether substitute workers the company called in are legal.
Like gold, fewer and fewer large copper deposits are being discovered, and the time between discovery and production has lengthened over the years as costs rise.
Shanghai copper price registered a second consecutive month of gains on Monday as prices firmed on a potential supply threat in Chile and massive US infrastructure spending plans.
The coronavirus pandemic highlighted the importance of securing supplies on a regional level and further strengthen western countries’ desire to end reliance on China.