Copper sulfide

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Copper sulfide corrosion
MFA# 22.407


Black corrosion details
MFA# 22.407

Dark blue hexagonal crystals or black powder. Copper sulfide occurs in nature as the blue mineral Covellite, that turns black in air. It is used in antifouling paints and in textile dying with Aniline black. Copper sulfide was probably used as a black pigment in antiquity (Orna et al 1980). Spots of black copper sulfide can sometimes be seen on corroded bronzes.

Synonyms and Related Terms

covellite (Pigment Blue 34; CI 77450;); cupric sulfide; indigo copper; kopersulfide (Ned.)

Raman spectrum of covellite
Image Credit:RRUFF


  • Irritating to skin and eyes.
  • Highly toxic by ingestion.
  • Can emit highly toxic hydrogen sulfide gas it exposed to high heat or acid.
Image Credit: RRUFF

Physical and Chemical Properties

Soluble in nitric acid. Insoluble in water, ethanol, dilute acids, alkalis.

Composition CuS
Mohs Hardness 1.5 - 2.0 (covellite)
Melting Point 220 C (dec)
Density 3.9-4.6 g/ml
Molecular Weight mol. wt. = 95.61

Resources and Citations

  • M.V.Orna; M.J.D.Low, N.S.Baer, "Synthetic Blue Pigments: Ninth to Sixteenth Centuries. I. Literature" Studies in Conservation, 25:53-63, 1980.
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Henry Hodges, Artifacts: An Introduction to Early Materials and Technology, Ronald P. Frye, Kingston, Canada, 1988
  • Monona Rossol, The Artist's Complete Health and Safety Guide, Allworth Press, New York, 1994
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 2724