The Al-bearing phases with orthorhombic (phase CF) and hexagonal (phase NAL) structures were observed in the system of average Mid-Ocean Ridge basalt at pressures above 25 GPa. Structure and composition of these two phases are very similar. Moreover, they can coexist in the single experimental sample. Here we report data on chemical composition, structure, and stability fields of the Al-bearing phases NAL and CF and investigate their relationship in the lower mantle.
