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ly. The oxygen fugacity (/02) of the experiments was not buffered externally. However, /02 calculations based on biotite-sanidine-magnetite-H20-02 equilibrium [D. R. Wones, Kozan Chishitsu 31, 191 (1981)] yield /02 values 1.5 to 2 log units above the nickel-nickel oxide buffer. This is consistent with the estimated f02 conditions of natural epidote-bearing magmas {6, 16). Quenched experimental charges were sectioned longitudinally, polished, and examined with reflected-light microscopy and backscattered electron imaging. Rim widths were measured with an optical microscope equipped with a graduated ocular lens; the rim widths reported are the average of 20 to 30 measurements. Rim width data are as follows: experiment Ep-10, t = 51.17 hours, rim width = 2.74 ± 0.9 fjim; experiment Ep-12, t = 141.20 hours, rim width = 4.95 ± 0.8 fjtm; and experiment Ep-11, t = 378.78 hours, rim width = 8.18 £ 1.3 fjtm. 9. D. C. Rubie and A.