Hydrothermal Growth of Fayalite Crystals

Abstract

Fayalite single crystals without any detectable contamination of the ferric ion could be hydrothermally grown under the controlled reducing conditions.

The adjustment method of the reduced atmosphere established in the present work was found to be applicable for keeping the hydrothermal condition within the stability field of the ferrous ion. The morphology of the grown fayalite crystal was affected by the grown temperature, the concentration of NaOH solution and the oxygen fugacity. The lower the growth temperature, the more remarkable become the developments of {021} and {110} faces and the diminishment of the {100} and {111} faces. It was also found the same effects of the concentration of NaOH and oxygen fugacity.

The results obtained in this experiment will be useful for the growth of larger and highly qualified fayalite crystals with a large-sized pressure vessel.

This work was done at the Laboratory for Hydrothermal Synthesis. Tokyo Institute of Technology.