Geography of Illinois before the dinosaurs. Galena, a lead ore, has been mined in the northwest corner of the state. The ore was processed around Peru, Illinois, where river transport was available to bring the ore to a source of coal. About six tons of coal are needed for each ton of ore. Fluorite, calcium fluoride, is the state mineral. It is mined in the southeastern portion of the state, around Metropolis. Fluorine gas is produced from fluorite. This is used in the production of uranium hexafluoride in Metropolis, Illinois for use at the gaseous diffusion plant in Paducah, Kentucky. Geodes can be
Schlangenberg Nature Reserve the surface where erosion removed large amounts. About 200 million years ago aqueous metal solutions filled the cavernous rocks. Primary ores were created mostly consisting of Sphalerite, Marcasite and Galena. The process continued and the ore close to the surface decomposed due to the influence of carbon dioxide and water. In this process as a secondary ore calamine ZnCO which is known as calamine developed. Presumably the Celts had been the first digging for the calamine in the region. Ancient Celtic and Roman coins dated between 100 BC and 92/93 AD as well as remains of a Roman settlement proved