1. Chamberlin, R. T., Carnegie Inst. Wash. Pub. No. 106 (1908).
2. Shepherd, E. S., Amer. J. Sci., 35, A, 311 (1938).
3. Emmons, R. C., Amer. J. Sci., 262, 561 (1964).
4. Preisinger, A., and Huber, W., Fortschritte der Mineralogie, 41, 183 (1964).
5. Wager, L. R. (private communication).