Cubic zirconia
Cubic Zirconia, CZ for short, is a synthetic
gem composed of
zirconium oxide, ZrO
2. It has a cubic crystal system, a
refractive index of 2.15-2.18,
dispersion of 0.065 (high),
specific gravity of 5.6-6,
hardness of 8.5, an adamantine
lustre, yellow-green to yellow
luminescence in short wave
ultraviolet light and whitish luminescence in long wave ultraviolet.
Zirconium is quite refractory, thus a special mechanism called a skull crucible is used to produce cubic zirconium.