290 University of California Publications in Geology [Vol. 11 



a remarkable tendency toward lenslike development. The lenses 

 are often rather thick, two to three feet being not uncommon, and 

 tend to approach a nodular character. In all cases the lenses or 

 nodules lie parallel to the bedding of the surrounding rock whether it 

 is chert or white shale. 



Both types of chert contain much less silica soluble in caustic 

 potash, than do the diatomaceous earths and bituminous shales. In 

 cherts only three or four per cent of the silica is soluble in caustic 

 potash. Their silica content ranges from eighty-five per cent to 

 ninety-five per cent silica. 



ANALYSES OF CHEETS AND SHALES 



The following table gives analyses of cherts and shales of the 

 Monterey formation : 23 



I. White porcelain shale, easily scratched with a knife and breaks with a con- 

 choidal fracture. Fairbanks, Univ. Calif. Publ., Bull. Dept. Geol., 

 vol. 2, p. 13, 1896. 



II. Analysis of a chalky shale from Carmelo Bay. Lawson and Posada, ibid., 

 vol. 1, p. 25, 1893. 



III. Analysis of an ' ' opaque flint. ' ' 



IV. Analysis of a " clear black flint. ' ' 



V. Soft white diatomaceous shale, Graeiosa Bidge, Santa Barbara County. 

 VI. Soft white diatomaceous shale, Purisima Hills, Santa Barbara County. 

 VII. Soft white diatomaceous shale, San Julian Kanch, Santa Barbara County. 

 VIII. Soft white diatomaceous shale, two miles south of Casmalia, Santa Barbara 

 County. 



IX. Gray glassy porcelain shale from same hand specimen as no. 8. 

 X. Hard black clear flint near Zaca, Santa Barbara County. 





I. 



II 



III 



IV 



V 



VI 



VI VIII IX X 



SiOa 



86.92 



86.89 



92.37 



98.1 



72.50 



65.62 



83.19 80.59 92.88 97.02 



A1 2 3 



4.27 ' 



2.32 



2.46 





11.71 







Fe,0 3 





1.28 







2.35 







CaO 



1.60 



.43 



1.70 





.32 







MgO 



trace 



trace 







.83 







K = 



Na 2 1 



I 2,48 ' 

 \ 1 



; i.26] 



i 2.32j 







1.88 







H,0 @ -i 

















100°C. 

 H,0 igni- 



> 5.13 



4.89 



2.74 





9.54 



11.00 





tion J 

















100.40 



99.39 



99.27 





99.13 



76.62 





Specific 

 gravity 



2.12 



1.8-21 



2.54 



2,57 









2 3 Analyses v, vi, vn, vin, ix, and x are given by Arnold and Anderson, in 

 IT. S. Geol'. Surv. Bull. 322, p. 45, 1907. 



