AbstractThe crystal structure of Fe₂SiO₄ spinel at room temperature was investigated at seven different pressures by X-ray diffraction, using a diamond anvil cell to examine the influence of Fe substitution on ringwoodite behaviour at high pressure. The results compared with those of a pure Mg endmember show that the substitution of Fe into the spinel structure causes only small changes in the compression rate of coordination polyhedra and the distortion of the octahedron. The data show that the compression rate for the octahedron and tetrahedron in (Mg,Fe)₂SiO₄ can be considered statistically equal for FeO₆ and MgO₆, as well as for SiO₄ in both the endmembers. This shows why almost identical bulk moduli are reported along the solid solution in recent literature.