VIII CONTENTS 



Gasconade formation 34 



Petrography 34 



Age and correlation 38 



Roubidoux fonpation 38 



Petrography 39 



Age and correlation 39 



Structure 40 



Folding 40 



Minor undulations 40 



Major folds 41 



Faults 42 



The Fertile area 42 



Stony Point area 43 



Time of the faulting 44 



Joints 45 



Geological History 45 



Geography and Geology of the Central District 49 



Geography 49 



Topography 50 



Drainage 50 



Geology 50 



The Gasconade formation 51 



The Roubidoux formation 52 



The Jefferson City formation 53 



Summary 54 



Economic Geology 55 



Mineralog}!' of the Barite Deposits 55 



Sulfids 55 



Chalcopyrite 55 



Galena 55 



Marcasite 55 



Pyrite 56 



Sphalerite 57 



Oxides 57 



Quartz 57 



Chalcedony 58 



Chert -; 58 



Limonite 58 



