Diamond vs Zirconia
Diamond and Zirconia are commonly confused, and 3 measured properties separate them — density most clearly.
Diamond vs Zirconia
These are different kinds of thing (mineral, compound). Fewer properties mean the same thing across both, so a like-for-like reading may not be available.
Diamond
C
Carbon in a cubic lattice — the hardest naturally occurring substance, and one of the best thermal conductors known.
Zirconia
ZrO2
A ceramic that resists cracking by changing crystal structure at the crack tip — and a convincing diamond substitute in its cubic form.
| Property | Diamond | Zirconia |
|---|---|---|
| Crystal system Only one of the two has a figure we can stand behind, so there is nothing to compare. | cubic | Not known |
| Density | 3.5–3.53 g/cm³ | 5.68–6.1 g/cm³ higher |
| Lustre Only one of the two has a figure we can stand behind, so there is nothing to compare. | adamantine | Not known |
| Melting point Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 2715 °C |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | 10 higher | 8–8.5 |
| Molar mass Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 123.22 g/mol |
| Refractive index | 2.417 higher | 2.15–2.18 |
| Thermal conductivity Only one of the two has a figure we can stand behind, so there is nothing to compare. | 900–2320 W/(m·K) | Not known |
Choosing between them
Zirconia is recorded as a substitute for Diamond — cheaper.
What it gives up: Softer, denser and it abrades over years of wear where diamond does not. As a gemstone it is a simulant rather than a substitute, and is not sold as anything else.
Partial substitute, on the evidence cited above.
Why these get confused
which is the entire commercial point of cubic zirconia, and it is separated instantly by thermal conductivity, which is what a jeweller's tester measures
The confusion is a real and documented one, not a resemblance we have invented.