Molybdochalkos

Molybdochalkos (Greek: Χαλκομόλυβδος,^[1] "copper-lead") is an alloy of copper and lead. It was the typical base metal used in the kerotakis, an alchemical invention credited to Mary the Jewess.

In Mary's writings, the "blackened lead" formed by exposing the alloy to sulfur vapors was considered an artificial decomposition, entirely separate from naturally black lead. This would form a basis for the alchemical process of blackening that would later be named nigredo.^[2]