Yes, sapphire glass can scratch, but it is incredibly resistant to scratches due to its exceptional hardness, making it one of the most scratch-resistant materials available outside of diamond.
Understanding Sapphire Glass Durability
Sapphire glass, often used in high-end watches, smartphone camera lenses, and other premium devices, is a synthetic material chemically identical to natural sapphire. Its primary advantage lies in its extraordinary hardness, which provides superior protection against everyday abrasions.
Hardness vs. Brittleness
It's crucial to distinguish between hardness and brittleness when discussing sapphire. While it might be exceptionally hard to scratch, sapphire is still brittle, meaning it can certainly chip or shatter upon a severe impact, especially at its edges. This characteristic is why you might see sapphire glass cracking from a drop even if it's virtually unblemished otherwise.
The Mohs Scale of Hardness
The Mohs scale is a qualitative ordinal scale from 1 to 10 characterizing scratch resistance of various minerals through the ability of a harder material to scratch a softer material.
Sapphire ranks at a 9 on the Mohs scale, placing it just below diamond (which is a 10). This high ranking means that only materials of equal or greater hardness can leave a permanent mark on its surface.
What Can Scratch Sapphire Glass?
Given its high Mohs rating, very few common materials can scratch sapphire glass. The primary culprits include:
- Diamonds: Ranking at 10 on the Mohs scale, diamonds are harder than sapphire and will easily scratch it. This includes industrial diamonds found in certain tools or diamond-studded jewelry.
- Silicon Carbide: Found in some specialized abrasives, grinding wheels, and even as tiny particles in some types of sand (though most sand, primarily quartz, is less hard than sapphire, sustained friction with it can still cause micro-abrasions over time).
- Other Sapphires/Corundum: Since sapphire itself is a form of corundum, another piece of sapphire or other corundum-based materials (like ruby, which is also corundum) could potentially scratch it.
Common Misconceptions
Many people believe everyday items like keys, coins, or even stainless steel can scratch sapphire. This is generally false:
- Keys and Coins: Typically made from steel or other softer metals, these rank much lower on the Mohs scale (around 5-6.5) and will not scratch sapphire glass. They might leave a residue that looks like a scratch but can often be wiped away.
- Glass and Quartz: Common glass (around 5.5) and quartz (7) are significantly softer than sapphire and cannot scratch it.
Sapphire vs. Other Glass Materials
To illustrate sapphire's scratch resistance, let's compare it with other common materials:
| Material | Mohs Hardness Scale (Approx.) | Scratch Resistance Level | Common Uses |
|---|---|---|---|
| Diamond | 10 | Extremely High (the hardest) | Jewelry, industrial cutting |
| Sapphire | 9 | Excellent | Watch crystals, camera lenses, high-end devices |
| Topaz | 8 | Very Good | Jewelry |
| Quartz | 7 | Good (standard glass is softer) | Watch crystals (mineral glass), sand |
| Gorilla Glass | 6-7 (varies by generation) | Good (enhanced for drop resistance) | Smartphone screens, tablets |
| Standard Glass | 5.5-6 | Moderate | Windows, bottles, basic device screens |
| Steel | 5-6.5 | Moderate | Tools, cutlery, some jewelry |
Note: Mohs hardness is a relative scale; specific values can vary slightly.
Practical Insights & Protection
While sapphire glass is remarkably scratch-resistant, it's not indestructible. Here are a few practical tips:
- Avoid Diamond Contact: Be mindful of jewelry containing diamonds, as these are the most common source of sapphire scratches.
- Beware of Abrasive Surfaces: Though rare, contact with industrial abrasives or surfaces laden with diamond or silicon carbide dust can pose a risk.
- Impact Protection: Since sapphire is brittle, ensure devices with sapphire glass are protected from severe drops or blunt force impacts, especially on edges, to prevent chipping or shattering.
- Cleaning: Use a soft, lint-free cloth, often dampened with water or a mild screen cleaner, to keep the sapphire surface pristine without causing damage.
In conclusion, while highly durable and extremely difficult to scratch, sapphire glass is not immune to damage. Its primary vulnerability lies in its brittleness, making it susceptible to chipping or shattering from impacts, and it can be scratched by materials harder than itself, notably diamonds.
