Al-rich pyroxene and melilite in a blast-furnace slag and a comparison with the Allende meteorite

Summary Fassaitic diopside containing 22–23 wt% Al2O3 (approximately 41–43% calcium Tschermak's molecule, CaAl2SiO6) and melilite containing 69–43% gehlenite crystallized from a blast-furnace slag at atmospheric pressure between about 1450°C and 1250°C. The occurrence is of petrological interest because the association of pyroxene with gehlenite-rich melilite has not been recorded from experimental studies in the system CaO-MgO-Al2O3-SiO2, and because of the similarity of the compositions of both minerals to pyroxene and melilite in the Ca-Al-rich inclusions of the Allende meteorite.