by Mike Lynch
(Sept. 27, 2013) — Homes and other structures that have been built on certain types of shale containing pyrite can suffer severe damages when the shale expands and heaves, according to research conducted at the University of Kentucky.
The problem of pyrite oxidation and shale expansion can be found worldwide, including East-Central Kentucky, where geochemist Warren Anderson of the Kentucky Geological Survey at UK has studied its effects.
A variety of organic and inorganic materials, such as clay, silt, trace metals and iron sulfide minerals, mainly pyrite, are found in the Chattanooga Shale formation across the state. When pyrite is exposed to moisture — during construction, excavation and rain — pyrite and other minerals oxidize and sulfate crystals form, growing to many times their original size. The result can be an acidic