1. Material Characterization Center, Report DOE/TIC-11400 (Pacific Northwest Laboratory, Richland, Washington, 1981).
2. T. BANBA, H. KIMURA, H. KAMIZONO and S. TASHIRO, Report JAERI-M82-088 (Japan Atomic Energy Research Institute, Ibaraki, Japan 1984).
3. H. KAMIZONO,J. Nucl. Mater. 127 (1985) 245.
4. H. KAMIZONO and H. NAKAMURA, ibid.152 (1988) 339.
5. A. N. WINCHELL, ?Elements of Optical Mineralogy? (Wiley, New York, 1951) pp. 106 and 150.