In a recent paper, Wu et al. (2005) claimed that they had found nanoscale TiO2 with the α-PbO2-structure in omphacite from a coesite-bearing eclogite at Shima in the eastern part of the Dabie Mountains, China. However, some results in their paper are questionable. First, the defects that were regarded as intercalated α-PbO2-type TiO2 lamellas by Wu et al. may be induced during the preparation process of rutile. Second, the SAED pattern in Figures 1b1, 2b2 and 3 from Wu et al. is not due to the diffraction of intercalated α-PbO2-type TiO2. Third, the lattice parameters reported by Wu et al. are too accurate to be derived only from HRTEM and SAED analyses. In this comment we show evidence for our doubts about their analysis.

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