The dzi beads in Ranwu Lake are jade dzi beads, which are sedimentary rocks of jade, agate and crystal minerals. At first, dzi beads were polished from conch fossils. Later, the number of conch fossils decreased, and people began to make dzi beads with agate. The dzi beads in Ranwu Lake have been oxidized by agate for more than 100 years or even longer, so the blue color of dzi beads is the oxidized color of agate.