8 Bulletin 9 . 200 



concretions and indurations again appear. This deposit con- 

 tains considerable quantities of iron pyrites, and the indurations 

 are often cut by veins of crystalline calcite. A short distance 

 below here is Calvert. Bluff/^ Robertson county, where lignite 

 occurs in large quantities and has been worked intermittently 

 for many years. The beds of this strata are shown in the 

 following section : 



1. Brown and red river silt 



2. Gray clay o 



3. Lignite 



4. Gray clay ^ 



5. Lignite 



6. Gray clay 



The clay beds in the above section contain large clay iron- 

 stone concretions, which enclose many leaf impressions. The 

 lignite is black, woody, friable, and of a dull lustre. It is 

 faulted and much jointed. Dip, three degrees southeast. From 

 here to where the International and Gieat Northern Railroad 

 crosses the river we see sand beds with calcareous indurations, 

 such as have been described at Rocky Rapids. At this point is 

 a bluff showing sixteen feet of Tertiary strata, capped by over 

 fifteen feet of a highly calcareous light green and 5^ellow Qua- 

 ternary clay containing many small white concretions. The 

 base of the Tertiary part of this bluff is composed of black 

 clay from the water edge up to ten feet above it, and is overlaid 

 by six feet of non-fossiliferous greensand marl. The Qua- 

 ternary lies uncouformably on the Tertiary strata. It is to be 

 seen at many points along the river from Falls county down, 

 and is doubtless the representative of an old river silt forma- 

 tion. For twelve miles below this point is seen a series of 

 interbedded and interlaminated clays and sands, with occasional 

 beds of lignite, and some few small gray calcareous concretions. 

 Frequently small fragments of lignite are seen in the sand beds, 

 showing that the swifter waters, which changed the charadler 

 of the bed from clay to sand, were also responsible for the 

 destrudtion of lignite beds, the fragments of which were depos- 

 ited with the sand. 



* The figure herewith given is from State Geologist Dvimble's work on 

 the Lignite or Brown Coal of Texas. 



