COMEX Copper soared near four year high amid sustained supply worries and steady equities. Prices have soared this week on concerns over supply disruption in Chile and a weaker dollar index. MCX Copper futures also witnessed a wild upswing to test highs above Rs 493 per kg levels. Copper gained impressively in the week after the union at BHPs Escondida mine in Chile, the worlds largest, said that it had started the latest round of wage negotiations. Failure to reach a deal last year triggered a strike that resulted in a near 8% drop in annual Copper output.BHP, which owns 57.5% of the mine, has spent nearly $ 8 billion expanding the mine (including a $ 3.4bn water plant) in the past five years to maintain output above one million tonnes (2018 guidance is 1.18-1.23mt). That means Escondida is responsible for nearly 5% of the worlds primary copper supply. The 2017 strike at Escondida was the longest in Chile since the 74-day action at state-owned Codelcos El Teniente mine in 1973, which took place shortly before the military coup that overthrew socialist President Salvador Allende.