Sapphire glass is exceptionally strong, particularly in terms of scratch resistance, due to its remarkable hardness.
Understanding Sapphire's Hardness
Sapphire, whether found naturally or created synthetically, is one of the hardest substances on earth. Its strength is often measured using the Mohs scale of mineral hardness.
The Mohs Scale
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.
| Material | Mohs Hardness |
|---|---|
| Talc | 1 |
| Gypsum | 2 |
| Calcite | 3 |
| Fluorite | 4 |
| Apatite | 5 |
| Feldspar | 6 |
| Quartz | 7 |
| Topaz | 8 |
| Sapphire | 9 |
| Diamond | 10 |
As the table illustrates, Sapphire measures 9 on the Mohs scale, which is a very high rating. This means that only materials harder than 9, primarily diamond (which measures 10, the highest rating), can scratch sapphire.
Practical Implications
This high Mohs hardness means sapphire glass is highly resistant to scratches from everyday materials such as:
- Keys
- Coins
- Sand (which is primarily quartz, measuring 7 on the Mohs scale)
- Steel objects
This inherent scratch resistance makes sapphire glass a popular choice for applications where durability and clarity are crucial, such as watch crystals and camera lens covers on high-end devices.
While incredibly hard and scratch-resistant, it's important to note that hardness differs from toughness. Hardness relates to resistance to scratching, while toughness relates to resistance to breaking or shattering upon impact. Sapphire glass is very hard but can still be susceptible to breakage under significant impact, depending on its thickness and design. However, its primary strength lies in its superior ability to resist surface damage.
