Black copper definitions

Black copper

A very impure (85-90%) first smelting of copper prior to fire refining.
Found on http://www.metalbulletin.com/Glossary.html

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black copper

a regulus of 95-percent-pure copper, produced in a blast furnace by smelting oxidized copper ores.
Found on https://www.infoplease.com/dictionary/black-copper

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