avoid serious damage to these structures as a result of swelling pressures. Some 

 clay-containing shales have the tendency to break down into mud upon re- 

 wetting if they are permitted to dry out. Foundation analysis would make it 

 possible to prevent serious damage in such cases. A closely related problem 

 was the occurrence of laumontite in foundation rock which upon exposure to 

 air was transformed into leonhardite. The loss of water had made the rock 

 very soft and friable. 



With X-ray diffraction methods it is possible to follow changes in soils, 

 shales, clay minerals, minerals, etc., that occur as a result of calcination. This 

 enables us to analyze ceramic materials and learn what optimum conditions 

 are required to produce top-grade products rather than products of mediocre 

 or unsatisfactory grades. Such knowledge also enables us to select suitable, 

 or to discard unsatisfactory, raw materials and shows us which raw materials 

 are satisfactory for specific purposes as in the production of light weight aggre- 

 gate, or how unsatisfactory raw materials can be upgraded by the addition of 

 certain substances or minerals. With such studies we can easily follow the reason 

 for changes in behavior that result from various calcination procedures and in the 

 past have been able to show that unsatisfactory products were the result of 

 faulty processing equipment. Such knowledge, likewise, enabled us to predict 

 which materials were satisfactory for the production of pozzolanic materials 

 and gave a method for analyzing the finished products. With this knowledge we 

 have been able to produce materials by which expansion in concrete due to 

 alkali-aggregate reaction was reduced by 95 percent. 



X-ray diffraction methods, likewise, enabled us to follow mineralogic 

 changes due to hydrothermal alteration of rocks which produced ore bodies. 

 Generally we found the sequence, ore body, sericite zone, kaolinite zone, mont- 

 morillonite zone, chlorite zone and unaltered rock as we moved outward from the 

 ore body in selecting our samples. This knowledge now permits us to study 

 ore-bearing areas through systematic sampling by means of drillcores and by 

 means of the alteration sequence learn where suspected ore bodies should be 

 located. 



This method of investigation also is being used extensively to support 

 stratigraphic correlations. In such studies members of formations are traced 

 and identified from one outcrop to another. 



Thus, after reviewing a number of solved problems it should become obvious 

 that X-ray diffraction methods of analysis of geologic materials can be used in 

 subsurface investigations to supply the geologist with information not otherwise 

 obtainable, to furnish the petroleum engineer with precise knowledge of the 

 composition and certain properties of reservoir rocks, and to trace mineralogic 

 and structural changes of importance in problems of sedimentation and sedi- 

 mentary petrology. 



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