Abstract: After the previous emergence of Gd₂O₃-doped colourless high-density synthetic cubic zirconia with a relative density of 6.60, a Yb₂O₃-doped colourless high-density synthetic cubic zirconia (abbreviated as CZ) with even higher density has appeared on the market. In this study, systematic analysis was performed on the Yb₂O₃-doped colourless high-density CZ via conventional gemmological tests, infrared spectroscopy, X-ray fluorescence (XRF), X-ray powder diffraction, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results showed that the sample has a relative density of approximately 7.40, which is significantly higher than that of both conventional CZ and Gd₂O₃-doped colourless high-density CZ. X-ray diffraction analysis indicated that its pattern is basically consistent with the standard diffraction pattern of cubic zirconia, confirming its cubic phase. Meanwhile, XRF and LA-ICP-MS data revealed that the mass fraction of Yb₂O₃ in the sample is as high as 50.91%-54.56%, with the corresponding chemical formulas of (Zr_0.62Yb_0.50)O₂, (Zr_0.64Yb_0.48)O₂ and (Zr_0.64Yb_0.49)O₂, respectively. The contents of the other elements are relatively low, so Yb is inferred to be the stabilizer, which differs from conventional CZ stabilized by Y₂O₃ and the high-density CZ stabilized by Gd₂O₃. It is further inferred that the high density induced by Yb₂O₃ doping mainly stems from the relatively high atomic mass of Yb. In addition, with the rapid surge in gold prices, some merchants take advantage of its high-density feature to seek profits by falsifying the weight of jewelry, which should arouse consumers' vigilance.