NOTE ON AN OCCURRENCE OF BLENDE IN 



LIGNITE. 



H. A. Wheeler, E. M. 



(Bead at the meeting of Academy of Science, of November 19, 18M.) 



In excavatiDg for the foundations of the new high-service 

 pumping-station at Baden, in North St. Louis, fragments of 

 blende-bearing lignite were found in the ♦' Ferruginous Sand- 

 stone " at a depth of about 25 feet. The pit is in the river- 

 bottom at the base of the bluffs that mark the western edge 

 of the valley of the Mississippi river, being about half a mile 

 west of the present river-bank, and furnishes the following 

 section : — 



Black "Gumbo" Soil 2' to 3'^ Recent. 



Fine Sand 12' to 18' I (Mississippi River) 



Coarse Sand and Pebbles 2' to 8' J Deposits. 



Grav to Drab Sandstone 2' to 10'") „ . „ ^ ^. 



„ ,; ^, , ,,.«,« Base of Coal Meas- 



Yellow Shale 1' to 2' ^ -^ 



Green Shale 2' to 3' J "''^** 



St. Louis Limestone — average depth, 32' ^ Suh- Carboniferous. 



The excavation stopped at the limestone, on which the coal- 

 measures rested unconformably. 



The sandstone in which the fraorments of lignite occurred 

 was coarse-grained, porous, cross-bedded, light-gray to dai'k- 

 drab in color, and rich in lignitic streaks with occasional 

 fragments several inches in thickness. Some of these frag- 

 ments of lignite or brown-coal are full of longitudinal and 

 transverse desiccation cracks, which are completely filled with 

 a ciystalline mixture of sphalerite or zinc-blende, calcite and 

 pyrite. The blende decidedly predominates, forming thin 

 seams -^^ to \ inch in thickness through the lignite, and 

 is light to dark brown in color, has a perfect cleavage, and the 

 usual resinous fracture. Calcite, of the white, crystalline 



(123) 



