LEAD AND ZINC. 16? 



Creek, Short Creek, Turkey Creek, and Center Creek, while from 

 the west come the Brush, Shawnee, and Cow creeks, all in Kansas. 

 Along the first mentioned creeks the principal mining towns are 

 situated, but others are found on the minor streams. They extend 

 through an area fifteen miles broad from east to west and twenty- 

 five miles from north to south. Newton and Jasper aTe the most 

 productive counties in Missouri, while Cherokee County, in Kansas, 

 also contains notable mines. Undeveloped districts are recorded in 

 Arkansas, but apparently at a lower geological horizon. The ore 

 occurs in the Keokuk or Archimedes limestone of the Lower Car- 

 boniferous. A generalized section of the rocks, according to F. L. 

 Clerc, is as follows. On the higher prairie, some 15 feet of 

 clay or gravel ; 10 feet of flint or chert beds ; 40 *feet of lime- 

 stone with thin beds of chert ; 60 feet of alternating layers of 

 limestone and chert; 100 feet and more of chert, sometimes chalky 

 with occasional beds of limestone ; 225 feet in total. In basins 

 and extensive pockets in these rocks, deposits of slates with small 

 coal seams are found, of undetermined geological relations. The 

 large bed of limestone of the section affords a datum of reference 

 in relation to which the ores may be described. A few minor, 

 shallow deposits occur in the flints over it. In the limestone the 

 ores are associated with a gangue of dolomitic clay and residual 

 flint. They occupy irregular cavities or openings, locally known 

 as circles, spar openings, and runs. (Clerc.) Below the limestone 

 the ore is found in " sheets, bands, seams, and pockets," and filling in 

 the interstices of a breccia of chert, which has been formed by the 

 breaking down of the chert layers on the solution and removal of 

 the interbedded limestones. There are districts where the over- 

 lying bed of limestone has also disappeared, and they then lack 

 it for a capping. The deposits extend to considerable depths be- 

 low the position of the limestone. The present mines have not 

 demonstrated as yet their limit of depth. At times the ore is 

 associated with a later formed quartz rock that has coated and 

 filled the cavities of the breccia. 



2.06.07. The removal of the interbedded layers of limestone 

 and the caving in of the associated cherts have been the principal 

 causes of the formation of cavities. Adolph Schmidt referred the 

 shrinkage to the dolomitization of pure lime carbonate, an idea 

 that has had extended adoption, and has also had an important 

 part in causing the general porosity. Schmidt traced five periods 

 in the geological history of the ore bodies: 1. Period of deposition 



