Powder X-ray diffraction analysis and Micro-Raman spectra were used to study the mineral composition of Chinese freshwater cultured pearls from Zhuji, Zhejiang Province. The results show that the pearls mainly contain aragonites, with some commercially useless pearls having vaterites in addition to aragonites. In pearls, the nacreous layers are generally translucent and composed completely of aragonite, whereas layers without pearly luster are opaque and composed of aragonites and/or vaterites with their relative concentrations different in different pearls. In conclusion, the freshwater cultured pearls produced by mussel Hyriopsis cumingii contain no calcites, and this is obviously different from characteristics of saltwater cultured pearls.