Cubic Zirconia

Cubic Zirconia: Zr02 mixed with Yttrium Oxide (Y203) or Calcium Oxide (CaO) as a stabilizing agent. Refractive Index:2.16; Relative Density:6; Dispersion:0.060; Hardness: 8.5. Introduced in 1977, the similarity with the figures for diamond make this the second best simulant produced to date, second only to a new type of stone called Moissanite.

Cubic Zirconia is an artificial synthetic because the stabilizing oxides used in its manufacture remain in the finished product and its structure is different to the natural material Baddeleyite Zr02. This has been such a good imitation that cubic zirconia can be purchased in both graded colours and clarities. Its refractive index is near enough for the stone to remain quite brilliant when tilted, and although the dispersion is higher than that of diamond, is not so obvious to the layman, and close enough to deceive. The relative density is much higher than diamond and a loose stone will appear to weigh too much. If set, it is easy to destructively test the stone with a diamond hardness pen.

Properties
Refractive Index (Brilliance) Dispersion (Fire)
Luster
Mohs Hardness
Toughness
Specific Gravity
Synthetic Moissanite
2.65 – 2.69
0.104
20.4%
9.25
Excellent
3.21
Diamond
2.42
0.044
17.2%
10
Good
3.52
Cubic Zirconia
2.17
0.066
N/A
8.25
Good
5.80
Sapphire
1.77
0.018
7.4%
9
Excellent
4.00
Emerald
1.58
0.014
4.8%
7.5
Good to Poor
2.72

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