1. Bentor, Y. K., Gross, S., and Heller, L., Amer. Min. (in the press).
2. Murdoch, J., Amer. Min., 46, 245 (1961).
3. Tilley, C. E., and Harwood, H. F., Min. Mag., 22, 439 (1931).
4. Tilley, C. E., Min. Mag., 23, 419 (1933).
5. McConnell, J. D., Min. Mag., 30, 293 (1954); 31, 798, 801 (1958).