Differences between Cubic Zirconia and Diamond
Contents
Cubic Zirconia vs. Diamond
Cubic zirconia and diamond are two distinct gemstones that appear similar to the naked eye but possess fundamentally different chemical, physical, and optical properties.[1][2] A diamond is a naturally occurring mineral composed of carbon atoms arranged in a crystal lattice structure.[3][4] Cubic zirconia (CZ) is a synthetic, lab-created gemstone made from the cubic crystalline form of zirconium dioxide (ZrO2).[5] While CZ was developed as a low-cost diamond simulant, key differences in durability, optical characteristics, and value distinguish the two.[1]
Comparison Table
[1]| Refractive Index || 2.15–2.18 || 2.42[2]| Category | Cubic Zirconia | Diamond |
|---|---|---|
| Composition | [5]| Carbon (C) | |
| Origin | [1]| Naturally formed in the Earth's mantle or lab-grown | |
| Hardness (Mohs Scale) | 8–8.5 | 10[1] |
| Dispersion[2] ("Fire") | 0.058–0.066 | 0.044 |
| Density[2] | Heavier than a diamond of the same size | Lighter than a cubic zirconia of the same size |
| Thermal Conductivity | Thermal insulator | Thermal conductor |
| Price[3] (per carat) | Approximately $20 | Varies,[5] starting from ~$1,500–$1,800 |
Durability[5]
One of the most significant differences between the two gemstones is their hardness. Diamond is the hardest known natural material, ranking a 10 on the Mohs scale of mineral hardness. This makes[1][3] it highly resistant to scratching and suitable for daily wear. Cubic zirconia[1] has a Mohs hardness of 8 to 8.5. While durable,[1] it is more susceptible to scratches and abrasions over time, which can cause it to appear cloudy.
Optical[5] Properties
Although they may look similar, cubic zirconia and diamond handle light differently. A diamond's higher refractive index of 2.42 gives it a greater level of brilliance (the reflection of white light). Cubic zirconia[2] has a lower refractive index of 2.15–2.18.
However, cubic[2] zirconia has a higher dispersion rate (0.058–0.066) than diamond (0.044). This means CZ separates light into a more pronounced rainbow-like effect, often referred to as "fire." While some find[1][2] this attractive, the excessive fire can make it look less natural than a diamond, which exhibits a more balanced display of brilliance and fire. Furthermore, nearly[1] all cubic zirconia is internally flawless, whereas most diamonds contain natural inclusions or imperfections.
Thermal Conductivity[1] and Density
Diamonds are effective thermal conductors, while cubic zirconia is a thermal insulator. This property allows jewelers to quickly distinguish between the two using a simple thermal conductivity tester. Additionally, cubic zirconia is denser than diamond. If a cubic zirconia and a diamond have the same carat weight, the diamond will appear larger, whereas if they are the same physical size, the cubic zirconia will be heavier.
Origin and Value
Diamonds are natural minerals that form under immense heat and pressure deep within the Earth's mantle over billions of years, though they can also be created in laboratories. In contrast, cubic[1][4] zirconia is a synthetic stone that has been commercially produced in labs since the 1970s.
This vast difference[1] in origin and rarity is reflected in their price. A one-carat diamond can cost thousands of dollars, depending on its quality. A one-carat cubic[5] zirconia, however, may only cost a few dollars. Cubic zirconia[1] has no significant resale value, whereas diamonds generally retain some market value.[5]
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 "brilliantearth.com". Retrieved January 22, 2026.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "shiels.com.au". Retrieved January 22, 2026.
- ↑ 3.0 3.1 3.2 "celinni.com". Retrieved January 22, 2026.
- ↑ 4.0 4.1 "impressjewelers.com". Retrieved January 22, 2026.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 "gsdiamonds.com.au". Retrieved January 22, 2026.
