Electrostatic potentials and Pauling bond strengths have been calculated for a group of oxygen and hydroxyl sites in high-pressure silicate and oxide phases. The O1 position in β-Mg2SiO4 more closely resembles a hydroxyl than an oxygen in its electrostatic potential and coordination. This raises the possibility that β-Mg2SiO4 may be a host phase for water in the lower part of the upper mantle, if charge balance can be maintained by partial M-site vacancy as is typical of high-pressure pyroxenes. Partial hydroxyl occupancy of O1 is consistent with synthesis experiments, crystal-structure analysis, and Raman spectroscopic data, but further experimental work is required to confirm and evaluate the significance of this possibility. If it can be demonstrated experimentally that this does occur, there would be substantial consequences for geophysical and geochemical models of the upper mantle.

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