Cubic zirconia (CZ) typically scores between 8 and 8.5 on the Mohs scale of mineral hardness. This makes it a relatively hard material, suitable for use in jewelry and various applications.
Understanding Cubic Zirconia Hardness
The Mohs scale is a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. Developed in 1812 by German geologist and mineralogist Friedrich Mohs, it ranges from 1 (talc, the softest) to 10 (diamond, the hardest).
Cubic zirconia's position on this scale highlights its durability and resistance to scratching from many common materials. For comparison, most semi-precious natural gems are slightly softer than cubic zirconia.
Key Properties of Cubic Zirconia
Beyond its notable hardness, cubic zirconia possesses other significant characteristics that contribute to its appeal and utility, especially as a diamond simulant.
- Refractive Index: Cubic zirconia has a high refractive index, typically ranging from 2.15 to 2.18. This property dictates how much light bends when it enters the material, significantly influencing its brilliance and sparkle. While high, it is slightly less than that of a diamond, which has a refractive index of approximately 2.42.
- Luster: The luster of cubic zirconia is Adamantine. This term describes a brilliant, diamond-like sheen, contributing to its sparkling appearance.
- Density: Cubic zirconia is also denser than diamond, meaning a cubic zirconia stone of the same carat weight will appear smaller than a diamond of equivalent weight.
Practical Implications of Cubic Zirconia's Hardness
The 8 to 8.5 Mohs rating for cubic zirconia has several practical implications for its use:
- Durability in Jewelry: Its significant hardness means cubic zirconia is quite resistant to everyday wear and tear. It can withstand scratches from common household dust (which often contains quartz particles, Mohs 7) and most metals, making it a durable choice for rings, earrings, necklaces, and other jewelry items.
- Maintenance: While durable, it's still advisable to store cubic zirconia jewelry separately from harder gems like diamonds to prevent scratching the CZ, and from softer gems to prevent the CZ from scratching them. Regular cleaning with mild soap and water can maintain its luster.
- Comparison to Natural Gems: Its hardness surpasses that of many popular natural gemstones, making it a resilient alternative.
To summarize the properties of Cubic Zirconia:
| Property | Value |
|---|---|
| Mohs Hardness | 8 – 8.5 |
| Refractive Index | 2.15 – 2.18 |
| Luster | Adamantine |
| Relative Hardness | Slightly harder than most semi-precious natural gems |
