Deep-Sea Worm Produces Orpiment, a Toxic Yellow Pigment Used in Historical Art

image via New Scientist

August 28, 2025, 5:00 PM

• •A deep-sea worm, *Paralvinella hessleri*, is the first animal known to create orpiment.
• •Orpiment is a toxic, arsenic-containing mineral used by artists for centuries.
• •The worm accumulates arsenic on its skin, which reacts with sulfide to form orpiment as a protective armour.
• •Researchers are studying how arsenic is transported into the worm's internal organs.

A bright-yellow deep-sea worm, *Paralvinella hessleri*, has been discovered to create orpiment, a toxic arsenic-containing mineral. This mineral was used by artists for centuries. The worm lives in hydrothermal vents, where it accumulates arsenic on its outer skin. This arsenic reacts with sulfide to form a protective microscopic armour of orpiment. Further research aims to understand how arsenic is transported within the worm.

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