Aggregates composed of pentlandite, isocubanite and pyrrhotite occur in the basaltic andesite from Kasayama volcano, Hagi-city, Yamaguchi Prefecture, Japan. Fe content of pentlandite is slightly over the value of ideal formula (Fe4.5Ni4.5S)8. Isocubanite is close to the ideal CuFe2S3. The aggregates of these sulfides may have been crystallized from sulfide melt having composition of pentlandite solid-solution in silicate melt. After that, pentlandite solid-solution exsolved to pentlandite and Cu-Fe-S intermediate solid solution (iss). The iss also exsolved to isocubanite and pyrrhotite.
