The Extraordinary Variety and Complexity of Minerals in a Single Keokuk Geode from the Lower Warsaw Formation, Hamilton, Illinois, USA

We performed an extensive optical and chemical analysis of a single Keokuk geode using electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy that revealed extraordinary array minerals multiple, complex cycles mineralization. identified at least 15 including 5 that, to our knowledge, have not been reported in previous studies these geodes. Along bitumen we described the occurrence REE’s, other unidentified phases containing metals such as chromium, nickel, molybdenum, tin, copper, zinc, lead. Additionally, preliminary thin-section reveals tentatively zircon, rutile, xenotime well grains gold silver within chalcedony shell. The presence potentially economically valuable warrants further investigation into micro-minerology Our SEM/EDX mineral assemblages, intergrowths, inclusions help chronologically link multiple stages paragenesis occurring different locations geode. Consequently, morphology intricate microstructures provide window extreme complexity crystallization. majority micro-minerals observed correspond later paragenesis, thus providing detailed record secondary mineralization processes which occurred over thousands millions years.