In 2024, a previously undocumented synthetic cubic zirconia product, traded as "heavy-zircon", emerged in the Wuzhou gem market (Guangxi, China). To address the lack of peer-reviewed data on its composition and identity, we performed a comprehensive mineralogical and gemological study using electron-probe microanalysis (EPMA), X-ray diffraction (XRD), fourier-transform infrared (FTIR), and micro-Raman spectroscopy. The material has a high relative density of approximately 7.40 and is primarily composed of Yb₂O₃ (51.08%~53.06%) and ZrO₂, with minor Y₂O₃. Its elevated density results from the incorporation of ytterbium (Yb), a heavy rare earth element. Single-crystal XRD confirms an isometric fluorite-type structure (space group Fm3m) with a lattice parameter a=5.134 8(18) Å and a unit-cell volume V=135.39(8) ų. The calculated chemical formulas are Zr_0.57Yb_0.40Y_0.03O_1.78□_0.22 or Zr_0.59Yb_0.41O_1.79□_0.21 (□ denotes oxygen vacancy). These results identify heavy-zircon as a high-density, ytterbium-rich variant of yttria-stabilized cubic zirconia. In accordance with gemological nomenclature, we propose "synthetic ytterbium-rich cubic zirconia" as its formal species name.