Abstract: Blue chalcedony is a special local gemstone in Taiwan. Taiwan blue chalcedony owes beauty and popularity to its vivid blue-greenish blue color and its value is the highest among the jade from Taiwan. It also outshines others in the world market. Blue chalcedony from Taiwan was found in Haian Mountain Range of east bank of Taiwan island, and its occurence belongs to hydrothermal deposit. The blue chalcedony from Taiwan is compared with its simulants in detail.