The Alchemical Symbol for Dead Matter

Ancient alchemists used the term Caput mortuum to describe useless leftovers from experiments. To represent this decay, they literally marked these worthless residues with a skull icon.

This Latin phrase translates to dead head and served as a bleak reminder of failed chemical transformations. While it began as a way to discard scientific waste, the term eventually became a way to describe things that had lost their original value or essence. Interestingly, the label was also used by painters to describe a dull, brownish-purple pigment derived from iron oxide. It remains a fascinating example of how scientific failure was once woven into the language of death.