Copper and iron were most commonly used as both are tough and easily shaped.

铜和铁使用最为普遍，因其坚固且易于塑形。

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While China remains the major player in copper, 2012 will be a tough year.

FORBES: Higher Copper Output Expected In 2012, Imports Will Slow -- Jones

We face a tough six to eight months, but towards the end of the year we should touch bottom on copper, aluminum and zinc.

CNN: Money & Investing