Host: Japan Association of Mineralogical Sciences
Chromian epidote occurs rarely in nature. This study is the first report for synthesis and structural refinement for synthetic Cr-epidote. Experiments were conducted at 0.35-0.4GPa and 500°C for oxide mixture, and 0.8-1.5GPa and 500-800°C for gel starting material. Cr-epidote was successfully synthesized as predominant phase from the gel staring materials. The crystal structures were refined by X-ray Rietveld method. The cell parameters increase with increasing Cr content. Cr3+ shows stronger preference for M3 than M1, but M1 preference of Cr3+ is stronger than that of Fe3+ and Mn3+. The experimental result implies that Cr in the amorphous gels played an essential role for the crystallization of Cr-epidote. The source material of the transition elements is an essential factor for the genesis of epidotes.
