CHARACTERIZING AND TREATING PYRITE DISEASE IN FOSSIL INVERTEBRATES

The U-M Museum of Paleontology Invertebrate Paleontology collection is home to approximately 2 million fossil specimens. Approximately 50% of this collection is from the Middle Devonian (~393-382 million years ago) with a specific emphasis on the Silica Shale Formation, which outcrops in Michigan and Ohio. The Silica Shale is known for its well preserved specimens that have been replaced from their original shell material to pyrite. Over time, pyrite oxidizes and if stored in sub-optimal conditions will spread like a disease or fungus. A primary preventative measure is to isolate the specimens and store them in a low humidity environment. The environmental conditions are optimal and we have developed a characterization scheme for assessing the degree of pyritization, sulfate byproduct present, and viability for treatment options. We organized the specimens by geographic location and selected several to be examined using SEM and XRD analysis to better characterize the iron sulfide minerals. Specimens affected by the disease undergo mechanical and/or chemical treatments depending on the specimen and degree of decay. Here we present the work we have conducted thus far and current outcomes of treatment. There is no ‘cure’ for pyrite disease and it greatly affects natural history collections globally. Our work will provide a baseline for other collections to consider short and long-term treatment options for their afflicted specimens.