LEAD AND ZINC. 171 



posit is called a run. The runs are from 5 to 50 feet in height, 

 100 to 300 feet long, and 10 to 50 feet across. At Webb City 

 they are even larger. As a general thing the ore is in the inter- 

 stices of the brecciated chert, but it is also in limestone and dolo- 

 mite, and associated with a silicified form of the insoluble residue 

 left by the solution of the limestone, which Dr. Jenney calls 

 " cherokite." All the ores require concentration. Galena usually 

 occurs ifl^r the surface, while blende is more abundant in depth. 

 Cadmium is at times present in the blende in notable amount. 



2.06.08. Some interesting alterations of the minerals have oc- 

 curred, which have changed the blende to smithsonite and cala- 

 mine. In one case a secondary precipitation of zinc sulphide has 

 occurred as a white amorphous powder which is of very recent 

 date. With the original precipitation of the blende the asphaltic 

 material may have had something to do. In the matter of produc- 

 tion Dr. Jenney fixes the ratio of the blende, galena, and pyrite 

 at about 1000 : 80 : O.5. 1 



2.06.09. Other zinc and lead deposits are known in central 

 Missouri generally resembling the above quite strongly, but of 

 less economic importance. Some, however, are described by 

 Schmidt as conical stockworks. They sometimes are found in 

 Lower Silurian strata. 



1 G. C. Broadhead, "Geological History of the Ozark Uplift," Amer. 

 Geol, III. 6. H. M. Chance, "The Rush Creek (Arkansas) Zinc District," 

 Trans. Amer. Inst. Mm. Eng., Washington meeting, 1890. F. L. Clerc, 

 Geological description of the mines in a statistical pamphlet on the Lead 

 and Zinc Ores of Southwest Missouri Mines, p. 4, published by J. M. Wil- 

 son, Carthage, Mo., 1887. Rec. See also Engineering and Mining Jour- 

 nal, June 4, 1887, p. 897. " Zinc in the United States," Mineral Resources, 

 1882, p. 368. Engineering and Mining Journal, Nov. 3, 1888, p. 389 ; March 

 8, 1890, p. 286. E. Haworth, A Contribution to the Geology of the Lead 

 and Zinc Mining District of Cherokee County, Kansas, Oskaloosa, Iowa, 

 1884. C. Henrich, " Zincblende Mines and Mining near Webb City, Mo.," 

 M. E., February, 1892 ; Engineering and Mining Journal, June 4, 1892. 

 R. W. Raymond, "Note on the Zinc Deposits of Southern Missouri," M. 

 E., VIII. 165 ; Engineering and Mining Journal, Oct. 4, 1879. J. D. Rob- 

 ertson, "A New Variety of Zinc Sulphide from Cherokee County, Kansas," 

 Amer. Jour. Sci., iii., XL., p. 160. A. Schmidt and A. Leonhard, Missouri 

 Geol. Survey, 1874. A. Schmidt, "Forms and Origin of the Lead and Zinc 

 Deposits of Southwest Missouri," Trans. St. Louis Aead. Sci., III. 246; 

 Amer. Jour. Sci., iii., X., p. 300. Die Blei und Zink Erzlagerstatten von 

 Sudwest Missouri, Heidelberg, Germany, 1876. W. H. Seamon, "Zinc- 

 iferous Clays of Southwest Missouri/' Amer. Jour. Sci., iii., XXXIX., p. 38. 



