Habit of Metallic Iron in Experimental Glasses: Do You Believe Your Eyes?

An experimental study of the form of metallic iron deposited from silicate melt at a drastic fO2 decrease was conducted at 1400°C and 1 atm total pressure. The oxygen fugacity was controlled by CO/CO2 gas mixture. It was demonstrated that the metallic iron initially forms a network of euhedral crystals near the melt surface. With an increase in experimental duration, the iron loses its crystalline morphology. At a high magnification, it looks like being melted before quenching, although the experimental temperature was fixed at ca. 140°C below the melting point of pure iron. Experimental studies with similar results are reviewed.