614 W. A. NELSON VOLCANIC ASH BED IN THE ORDOVICIAN 



been altered immediately following eruption into a material somewhat 

 a km to levernerite. The material swells when put into water and breaks 

 down into a doughy mass with imbedded sand grains. It contains 

 feldspar and other minerals, chiefly leverrierite. 



Leverrierite is the mineral that swells in water and breaks up into a 

 doughy mass. The numerous other grains besides leverrierite appear to 

 be angular, broken, embayed crystals, such as are found in volcanic ash, 

 the chief of which, from the optical properties noted, is probably soda 

 orthoclase. In addition to some quartz being present, there is consider- 

 able apatite, a very little zircon, and more or less colorless mica. There 

 are also grains that resemble the altered groundmass of a rhyolite and 

 some spherulitic aggregates that are probably chalcedony. 



In conclusion, Larsen states that the general character of the purer 

 samples submitted, as well as similarity to the bentonites of the west, 

 which have been shown to have that origin, 12 is that of an altered volcanic 

 ash in which the glass fragments have been changed to leverrierite. The 

 water is lower than in most leverrierites, but it is known that much of 

 the water in leverrierite is loosely held and does not appear to be essential 

 to the mineral. 13 



Analyses of Bentonite and Leverrieeite 









No. 1 



No. 2 



No. 3 



No. 4 



No. 5 



No. 6 



No. 7 



No. S 









Per 

 cent. 



Per 

 cent. 



Pet- 

 cent. 



Per 



cent. 



Per 



cent. 



Per- 

 cent. 



Pet- 

 cent. 



Pet- 

 cent. 



SiOo 







54.80 

 22.93 



54.56 

 19.97 



58.88 

 22.91 



55.28 

 24.65 



51.1 

 16.1 



64.00 

 22.9 



60.18 

 26.58 



47 56 



ALO, 







20.57 



FeA 

 FeO 







1.91 

 .45 



.69 



1.28 



.78 

 .86 



.51/ 

 1.08 \ 

 trace 



4.5 



3.1 





( 8.58 

 ) =24 

 1 2.52 



CaO 







1.20 



1.08 



trace 



5.2 



1.0 



.23 



MgO 







3.10 



5.08 



2.36 



3.71 



3.8 



2.0 



1.01 



.80 



P 2 5 







.13 

 .11 



.15 

 .13 



.17 

 trace 



.16 

 trace 













F 









K 2 



Na 2 

 H 2 







2.04 

 4.12 



4.06 

 1.66 



4.30 

 2.42 



3.71) 



2.06 ( 



1.5 





1.23 









1.28 



100° 



-110° c. 



4.58 



6.62 



3.34 



3.44 



13.1 







6.65 



H 2 



150° 



-160° c. 



.68 



.48 



.26 



.52 











H 2 



200° 



-210° c. 



.52 



.32 



.56 



.20 





7.00 



10.26 





H 2 



red 



heat. . . 



3.83 



4.52 



3.27 



4.77 



4.0 







10.95 



(1) Bentonite from road-cut on Dixie Highway at Singleton, Bedford 

 County, Tennessee ; analysis by D. F. Farrar. 



(2) Bentonite from High Bridge, Kentucky; analysis by D. F. Farrar. 



12 D. F. Hewett : Op. cit.. pp. 196-198. 



u Esper Larsen and Edgar T. Wherry : Leverrierite from Colorado. 

 Academy of Science, vol. 7, 1917, pp. 208-217. 



Jour. Washington 



