Nature of phases synthesized along the join (Mg,Mn)2Si2O6.

Eight compositions were synthesized along this join. Orthopyroxene crystallized at X = Mn/(Mn + Mg) = 0.0-0.3, clinopyroxene at X 0.4-0.5, and pyroxmangite at X 0.65-1.0, consistent with the composition ranges that have been inferred by examination of metamorphic rock assemblages. Unit-cell dimensions for these phases and for rhodonite (X = 1.0) are presented, along with microprobe chemical analyses and phase diagrams.-J.A.Z.