Imports of certain copper products into the US face a 50% tariff from Aug. 1 as President Donald Trump seeks to revive the domestic supply chain and make the country less reliant on foreign sources of this critical material.

The president stopped short of putting a 50 percent tariff on refined copper, as he had threatened earlier this year. The market reaction was swift anyway and prices tumbled.

The US copper market is scrambling to understand the implications of Trump’s tariffs, which the president said will help boost domestic output of semi-processed and copper-containing products.