Synthesis of bicchulite from gehlenite solid solutions

抄録

Bicchulite was synthesized from gehlenite solid solutions with a composition range from Ak₀Ge₁₀₀ to Ak₄₀Ge₆₀. Upper limits of the stability field of bicchulite at 1 kbar water pressure were found to be at 635°C for Ak₀Ge₁₀₀, 610°C for Ak₂₀Ge₈₀, and 605°C for Ak₄₀Ge₆₀. Gehlenite with the akermanite components less than 20% decomposes to bicchulite±idocrase±xanthophyllite below the temperature of the stability limit, while gehlenite with the akermanite component more than 30% breaks down at a temperature higher than the temperature of bicchulite stability, 630°C for Ak₃₀Ge₇₀ and 680°C for Ak₅₀Ge₅₀, forming idocrase+xanthophyllite±monticellite. Xanthophyllite obtained in the experiments is stable only at temperatures above about 400°C. Below that temperature it changes to hydrogrossular.
Some natural specimens were also studied for geological applications.