Study on Gemmological Character of Synthetic Colourful Cubic Zirconia

Purple, light purple, light yellow, pink, deep yellow, brown and red cubic zirconias have sub adamantine luster and their fire is obvious. Their density and relative hardness are 5.99~6.34 g/cm³ and 8~9, respectively. Pink cubic zirconia is anisotropic and a lot of white material distributes orientedly in it. The others are isotropic without any inclusions by magnified 40 times. Cubic zirconias with different colours have different absorption spectra and ultraviolet fluorescences and colours under filter. Absorption spectrum of light purple cubic zirconia indicates that Nd is its colouring element. The XRF analysis indicates that Zr, Y, P, Hf and Ca, etc, are common in colourful cubic zirconia and Er, Ce, Fe are colouring elements of pink, red, deep yellow cubic zirconias respectively. Cubic zirconia is isotropic when mol fraction of Y₂O₃ is more than 7% or nearly 7%, but cubic zirconia is anisotropic and there is a lot of white material oriented in it when mol fraction of Y₂O₃ is less than 5%. According to Glasden dell formula modified by Larsen, approximate refractive index is 2.12~2.19.