Subsurface Laboratory Methods 



199 



3. After step (2) , the acidized material must be completely dehy- 

 drated by drying for several hours at temperatures of about 105 ° C. 



4. About one milligram of the sample material should be used when 

 the stain solutions are applied. 



5. The treated sample should remain in the stain solution for five 

 minutes in order to obtain the best coloration results. 



6. The reflected light source should be controlled. 



Clay mineralogy offers possibilities for serving as a means of corre- 

 lating and subdividing homogeneous argillaceous and carbonate sections. 

 The latter rock types involve insoluble residues. Clay mineralogy can 

 also be useful in evaluating changes in the porosity and permeability of 

 sands and sandstones. 



The presence of montmorillonite clay types is extremely detrimental 



TABLE 7 

 Summary of Clay-Stain Results 



in many engineering projects because of their swelling properties. Sedi- 

 ments containing these minerals should be completely analyzed before 

 construction of buildings, highways, dams, and other projects in order 

 to predict the reaction of the earth materials. 



Shape Analysis 

 L. W. LeROY 



Various procedures are followed in determining the sphericity, round- 

 ness, and flatness values of sedimentary particles. 



Krumbein and Pettijohn^^ give the following factors controlling the 

 shape of sedimentary grains and fragments: (1) the original shape of the 

 fragment; (2) the structure of the fragment, as cleavage or bedding; (3) 

 the durability of the material; (4) the nature of the geologic agent; (5) 

 the nature of action to which the fragment is subjected and the violence 

 of that action (rigor) ; and (6) the time or distance through which the 

 action is extended. 



Varying degrees of sphericity ("measured by the ratio of 5/5, where 



°' Krumbein, W. C, and Pettijohn, F. J., Manual of Sedimentary Petrography, p. 278, New York, 

 D. Appleton-Century Co., 1938. 



