The crystal protects your dial from dust, moisture, and impacts. Three types exist: sapphire, mineral, and acrylic. Each has distinct advantages for different uses and budgets.
Quick Comparison
| Property | Sapphire | Mineral | Acrylic |
|---|---|---|---|
| Scratch Resistance | Excellent (9 Mohs) | Good (5-6 Mohs) | Poor (3 Mohs) |
| Shatter Resistance | Poor | Moderate | Excellent |
| Repairability | Replace only | Replace only | Can polish scratches |
| Cost | High | Low | Very low |
Sapphire Crystal
Synthetic sapphire (aluminum oxide) rates 9 on Mohs hardness—only diamond is harder. Virtually scratch-proof against everyday materials. Standard on watches over $300.
Pros
- Scratch-proof against normal wear
- Excellent clarity
- Stays pristine for decades
Cons
- Can shatter on sharp impact
- Expensive to replace ($50-200+)
Mineral Crystal
Hardened glass rating 5-6 on Mohs scale. Common on watches under $300. Adequate for casual use but will accumulate scratches over years.
Pros
- Inexpensive
- Better shatter resistance than sapphire
Cons
- Will scratch over time
- Cannot polish out scratches
Acrylic/Hesalite
Plastic crystal still used on vintage reissues and tool watches. The Omega Speedmaster Professional uses hesalite for NASA heritage authenticity.
Pros
- Shatter-proof (flexes, doesn't break)
- Scratches polish out with Polywatch
- Warm vintage aesthetic
Cons
- Scratches very easily
- Requires regular polishing
💡 The Speedmaster Choice
Omega offers the Speedmaster in both hesalite and sapphire. Purists choose hesalite for authenticity (NASA spec); pragmatists choose sapphire for durability. Both are valid—it's personal preference.
Which Should You Choose?
- Daily wear, desk work: Sapphire — stays pristine
- Active/outdoor use: Acrylic — won't shatter on impact
- Budget watches: Mineral — adequate protection at low cost
- Vintage authenticity: Acrylic — period-correct appearance