Mineralogical Characteristics of Ureyite in Jadeite Jade

In the paper, mineralogical characteristics and compositions of ureyite in jadeite jade are studied by using EPMA, X-ray diffraction and absorption spectroscopy analysis.The results show that ureyite is paragenous with jadeite jade, and the chemical formula of ureyite is(Na_0.83Ca_0.02)(Cr_0.78Al_0.10Fe_0.08Mg_0.02) Si_2.06O₆.The unit cell parameters of ureyite are a=9.530 Å, b=8.672 Å, c=5.264 Å, β=107.51°, V=414.88 and the density is 3.55g/cm³.Different shades of green in ureyite are related to the crystal-field transition frequency of Cr³⁺.