MINERALS 



1^ g 



4^*-^ 



%gf *^^ 





Fig. 14. Pyrite nodule, Chattanooga shale. 

 Fracture took place around rather than through 

 individual crystals revealing their pvritohedral 

 habit. X 16,700. 



Fig. 15. Step fracture of calcite crystal in 

 Solenhofen limestone. X28,000. (Courtesy of H. P. 

 Studer, Shell Development Company) 



facilitate study of a selected area of the sub- 

 ject with both light and electrons, the bound- 

 aries between the two disciplines are dis- 

 appearing and a more integrated picture is 

 being obtained of the entire mineral king- 

 dom. With the further development of ultra- 

 thin sectioning of hard and brittle substances 

 it is probable that no morphological feature 

 of minerals and mineral compounds will long 

 remain "invisible." 



REFERENCES 



1. Bates, T. F., Hildebrand, F. A. and Swine- 



ford, A., "Morphologj' and structure of 

 endellite and halloysite," Geol. Soc. Am. 

 Bull, 59, 1310 (1948); ^TO.MweraL, 35, 463- 

 485(1950). 



2. Comer, J. J. and Turley, J. W., "Replica 



studies of bulk clays," /. Appl. Phys., 26, 

 346-350 (1955). 



3. Bates, T. F. and Comer, J. J., "Electron mi- 



croscopy of clay surfaces," Natl. Acad. 

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 (1955) . 



4. Pfefferkorn, G., Themann, H., and Urban, 



H., "Anwendungen der mikrotomschnitt- 

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 raluntersuchungen," Proc. Stockholm Conf. 

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5. Maser, M., Rice, R. V., and Klug, H. P., 



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 680-688 (1960). 



6. Eitel, W. H., Muller, H. 0. and Radczew- 



SKi, O. E., "Examination of clay minerals 

 with the ultramicroscope," Ber. Deut. Keram. 

 Ges., 20, 165-180 (1938). 



7. Ardenne, M. von, Endell, K., and Hoff- 



mann, E., "Examination of the finest frac- 

 tions of bentonite and cement with the 

 universal microscope," Ber. Deut. Keram. 

 Ges., 21, 209-227 (1940). 



8. Humbert, R. P. and Shaw, B. T., "Studies of 



clay particles with the electron micro- 

 scope," Soil Sci., 52, 481-487 (1941). 



9. Endell, K., "Significance of the electron 



microscope for identifying the microstruc- 

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10. PiNSKER, Z. G., "Electrographic and elec- 



tronomicroscopic study of clay minerals," 

 Trudy Biogeokhim. Lab., Akad. Nauk SSSR, 

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11. Bates, T. F., "Electron microscopy as a 



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 Natl. Conf. on Clays and Clay Minerals, 



197 



