MISSOURI AND SOUTH-EAST KANSAS 889 



crystals adhering to pieces of broken Chert, sometimes on all sides ot the 

 fragments, showing plainly that the Galena was formed after the Chert had 

 been broken. 



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5 I Fourth Penod. — Local regeneration of the partially dissolved and softened 

 ^ -I Limestone by renewed deposition of Carbonate of Lime. Local 



a infiltration of Quartzite. Continued deposition of ores. 



All the conglomerates which consist of Chert-fragments, cemented either 

 by a silicious or by a calcareous mass, the cementing mass inclosing cryMtals 

 of Blende or Galena, were formed in this period. 



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Fifth Period. — Oxidation of tlie metallic Sulphurets, and alteration uf 

 Q i these Sulpburets into Silicates and Carbonates. 



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During this period the Galena, in many deposits, was more or less altered 

 into Cerussite and Pyromorphite, the Blende into Calamine and Smithson- 

 ite, and the Pyrites into Limouite. Same of these minerals also, while it 

 solution, were carried over larger or smaller distances and re-deposited as 

 seams or impregnations in Sands, in Clays or in Chert Breccia. 



The local corrosion and partial dissolution of the Chert, and its alteration 

 into a porous and more or less friable mass, must have taken place after the 

 deposition of the ores. This is proved by the entire absence of ores in the 

 poi'ous Chert. This corrosion, therefore, belongs to the Fourth and Fifth 

 Periods, and probablj' continues to the present da}". Also, the oxidation of 

 the ores undoubtedly yet continues. 



All these mechanical and chemical actions which, according to present 

 appearances, are confined to the upper layers of the Keokuk Limestone, have 

 taken place over a very large area in South-West Missouri, but with diffei'- 

 ent intensities and effects in different districts and localities." 



The stratifications in the Joj)lin district are generally ver}^ irregular in 

 their character and relative positions and often vary considerably within 

 short distances, the succession of rocku often remaining the same for long 

 distances but the layers being of veiy variable thickness and dipping with 

 the slopes. The materials in the bottom lands seem to be principally vast 

 deposits of sand, drift and chert, with occasional masses of Galena, known 

 as "float mineral." 



Owing to the exceedingly disturbed condition of the geological formik- 

 tions, it is almost impossible to form any opinion as to the existence or 

 non-existence of lead or zinc ores from any surface indications, any previous 

 experiences as a miner, or from any scientific teachings in the schools or 

 other raining regions, even in the same State. 



In the Joplin district the ore deposits are mostly to be found in "runs," 

 usually from one to five feet in thickness, extending horizontally between 



