Instability of Iron Sulfides on Recently Excavated Artifacts

Summary

The composition and nature of the different sulfides which can occur on underground iron are reviewed with reference to the literature, together with the various corrosion reactions. The type of pyrites on fossils and minerals is also included. The experimental work involved goethites and magnetites reacting with damp hydrogen sulfide gas to give mackinawite, pyrite and/or greigite. These can react exothermically and may be pyrophoric. Methods to increase stability and reduce the danger of pyrophoric oxidation are discussed.