Wheeler — Note on an Occurrence of Blende in Lignite. 125 



zinc region of Southwest Missouri, where the zinc occurs so 

 extensively in irregular bodies in broken chert and limestone 

 of Sub-Carboniferous age, is 250 miles southwest. 



Dr. W. P. Jenney* thinks that the zinc occurrences of the 

 Mississippi Valley are all of the same age, and that the source 

 of the zinc was from below. While the former idea of con- 

 temporaneous age may be possible, the occurrence of the 

 disseminated grains in the St. Louis limestone and in the 

 seams of the lignite in the Baden sandstone, decidedly show 

 that in at least these two cases the zinc was derived from 

 lateral secretion. The Baden sandstone, which is the equiva- 

 lent of the "Ferruginous " or at the base of the Coal Meas- 

 ures, also shows that the zinc was introduced at least as late 

 as the Coal Measure period, but not so recent as the Quater- 

 nary ; the lack of any formations between these horizons pre- 

 vents any closer determination of this question. 



The writer is indebted to Mr. J. Gordon Reel, C. E., the 

 engineer in charge of the work, for an excellent suite of the 

 blende specimens. 



* "Lead and Zinc Deposits of the Mississippi Valley." W. P. Jenney, 

 E. M. Transactions American Inst. Mining Engineers. Vol. 22. 



Issued February 21st, 1895, 



