MINERALS 



18. Castaing, R., "Proceedings of the Third Inter- 



national Conference on Electron Micros- 

 copy," p. 379 (London, 1954). 



19. Castaing, R., Rev. Met., 52, 669 (1955). 



20. Heidenreich, R. D., J. Appl. Physics, 20, 993 



(1949) . 



21. Bollmann, W., "Electron Microscopy: Pro- 



ceedings of the Stockholm Conference, 

 1956", p. 316. 1957, (Almqvist and Wiksell), 

 Stockholm. 



22. Bollmaxn, W., Phys. Rev., 103, 1588 (1956). 



23. Nicholson, R. B., Thomas, G. and Nutting, 



J., Brit. J. Appl. Physics, 9, 25 (1958). 



24. Tomlinson, H. M.,Phil. Mag., 3, 867 (1958). 



25. SwANN, p. R. AND Nutting, J., private com- 



munication. 



26. Brandon, D.G. AND Nutting, J., fin7. J. Appl. 



Physics, 10,255 (1959). 



27. MiRAND, P. AND Saulnier, A., Compt. rend., 



246, 1688 (1958). 



28. Michel, P., Sheet Metal Ind., 26, 2175 (1949). 



29. Fisher, R. M., private communication. 



30. Kelly, P. M. and Nutting, J., J. Iron Steel 



Inst., 192,246 (19-59). 



31. Nicholson, R. B., Ph.D. Thesis, Cambridge 



University'. 



32. SiLCOX, J. AND Hirsch, p. B., Phil. Mag., 4, 72 



(1959). 



33. Irving, B. A., Institute of Phj^sics Exeter 



Conference, 1959. 



34. Kerridge, J. F., Johnson, A. A. and Mat- 



thews, H. I., Nature, 184, 356 (1959). 



35. Saulnier, A. and Mirand, P., Compt. rend., 



247, 2351 (1958). 



36. Wilsdorf, H. G. F., Cinquina, L. and Vak- 



KER, C. J. Proc. Int. Conf. Electron Micr. 

 (in press) (1958). 



P. M. Kelly 

 J. Nutting 



MICROTOMY. See GENERAL MICROSCOPY, 

 p. 343. 



MINERALS 



The sizes, shapes and surface features of 

 minerals and mineral particles provide es- 

 sential and sometimes otherwise unobtain- 

 able information about such important sub- 

 jects as atomic structure, the nature of origin 

 and growth, and the reaction of minerals to 

 physical and chemical forces impo.sed either 

 by nature or man. Textural relationships of 

 minerals with other materials of their own 



or a different kind are often keys to the 

 nature of bonding forces and to the probable 

 behavior of the aggregate — be it rock, soil, 

 ceramic body, paint film, or drilling mud — 

 under the various conditions to which it is 

 subjected. 



Considered on the })asis of the size range 

 of mineral particles and their surface fea- 

 tures, one-third of the mineral kingdom was 

 "invisible" prior to the advent of electron 

 microscopy. The light microscope, penetrat- 

 ing to the tenths-of-a-micron region, leaves 

 unseen all objects measured in tens and hun- 

 dreds of Angstrom units; and although some 

 of these objects are reproduced in larger min- 

 eral particles, many ha^-e no counterpart in 

 the world of the light microscope or unaided 

 eye. Such, for example, are the detailed fea- 

 tures of tubular crystals of halloysite clay, 

 seen in replica in Figure 1, and of chrysotile 

 asbestos, shown in ultra-thin section in Fig- 

 ure 2. Until 1948 when the tubular form of 

 halloysite crystals was first revealed by the 

 electron microscope and the structure ex- 

 plained (1), it was not known that cylindri- 

 cal crystals with curved planes of atoms 

 existed as stable structures in the mineral 

 kingdom. In this and many other cases the 

 electron microscope removed the barriers 

 standing in the way of direct observation of 

 one of the most fertile parts of the mineral 

 kingdom, that lying beyond the realm of the 

 light microscope and bordered on the other 

 side by the land of measm-ement of the atoms 

 themselves. In mineralogy, therefore, as in 

 other fields, the electron microscope has two 

 functions : to serve as a supplement to the eye 

 and the light microscope by providing fur- 

 ther data on features visible at lower mag- 

 nification ; and to reveal to the eye the details 

 of objects indigenous to the 10 to 10,000 A 

 region. 



The ability of the microscope to perform 

 these functions has depended on the de\'elop- 

 ment of technique. Early mineralogical ap- 

 plications such as studies of mineral dusts, 

 clays, and pigments involved the morphol- 



187 



