Recent conflicting results on the mechanism of the olivine-spinel phase transition suggest that the mechanism varies with experimental conditions. Evidence for a shear-induced mechanism is strong in experiments performed at temperatures far from the melting point or under conditions where very large shear stresses may be inferred. Where temperatures are closer to the melting point and stress concentrations probably less severe, the evidence favors a nucleation and growth mechanism. In one study, volume reduction accompanied anion restacking and significantly preceded cation reordering, suggesting a change in bonding between the two polymorphs.