The postspinel mineral MgAl2O4 exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh2O4 exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 degrees C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl2O4 are absent in CdRh2O4. X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe2O4 structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl2O4. Replacement of Mg2+ with Cd2+ appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO3. In addition, Rh3+ could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched. from lower-pressure conditions.