What Is a Sapphire Crystal and Why Does Your Watch Need One?

What Is a Watch Crystal?

The watch crystal is the transparent cover that protects your watch dial from dust, moisture, and scratches. It sits on top of the case and is one of the most important components of any automatic watch. A good crystal makes your dial look sharp, while a bad one distorts colors and scratches easily.

At Funny Items, we offer watches with different crystal materials depending on the model. Here is what you need to know about each type.

Crystal Materials Compared

1. Sapphire Crystal

Sapphire crystal is the gold standard for watch crystals. It is made from synthetic sapphire — the same material used in watch jewels and high-end optics. On the Mohs hardness scale, sapphire scores a 9 out of 10, making it nearly impossible to scratch with everyday objects.

Key properties:

• Hardness: 9/10 (second only to diamond)
• Scratch resistance: Excellent — resists scratches from keys, coins, sand, and most materials
• Clarity: Superior — minimal distortion, excellent light transmission
• Weight: Heavier than mineral glass
• Cost: Most expensive option

AR coating: Many sapphire crystals have an anti-reflective (AR) coating that reduces glare and makes the dial easier to read in bright light. The coating is usually applied to the underside of the crystal.

See our sapphire-equipped watches: Meteorite NH34 GMT Watch, 43.5mm Relax Automatic Watch

2. Mineral Crystal

Mineral crystal is hardened glass. It is more scratch-resistant than regular glass but less resistant than sapphire. On the Mohs scale, it scores about 5-6. It will scratch from contact with sand, granite, or diamond.

Key properties:

• Hardness: 5-6/10
• Scratch resistance: Good — handles everyday wear but scratches from hard materials
• Clarity: Good — slight distortion possible
• Weight: Lighter than sapphire
• Cost: Affordable

Mineral crystal is the most common crystal in budget and mid-range watches. Most Funny Items watches ship with mineral crystal by default, with sapphire upgrades available on select models.

3. Acrylic / Hesalite Crystal

Acrylic crystal (also called Hesalite) is a plastic crystal. It scratches very easily but can be polished out with a simple compound. It is lightweight and shatter-resistant, making it popular for vintage-style watches.

Key properties:

• Hardness: 2-3/10
• Scratch resistance: Poor — scratches from almost anything
• Clarity: Warm, vintage look with slight distortion
• Weight: Very light
• Cost: Cheapest option

Crystal Shape: Flat vs Domed

Watch crystals come in two main shapes:

• Flat crystal — Sits flush with the case bezel. Clean, modern look. Less distortion.
• Domed crystal — Curves upward from the case. Vintage, dressy look. Adds slight distortion at the edges which many collectors love.

Funny Items offers both flat and domed options. The 39mm Vintage GMT NH34 uses a domed crystal for a retro feel. The 43.5mm Relax Automatic Watch uses a flat crystal for maximum clarity.

Sapphire vs Mineral: Which Should You Choose?

How to Tell What Crystal Your Watch Has

• The scratch test: Sapphire will not scratch from a steel knife. Mineral will leave a mark.
• The water drop test: Water beads tightly on sapphire due to its smooth surface. On mineral, the drop spreads more.
• Check the product description: All Funny Items watches clearly state whether the crystal is mineral or sapphire.

Crystal Replacement and Upgrades

Want to upgrade your watch crystal? Here is what you need to know:

• Crystal press: You need a crystal press tool to remove and install crystals
• Gasket: Always replace the crystal gasket when changing crystals
• Size matters: The new crystal must match the case opening diameter exactly

Funny Items offers sapphire crystal upgrades for select case models. Contact us for compatibility information.

Frequently Asked Questions

Can a sapphire crystal break?
Yes. Sapphire is scratch-resistant but can shatter from a hard impact. However, it is much more shatter-resistant than regular glass.

Does AR coating wear off?
AR coating can wear over years of cleaning and polishing. It does not affect the crystal itself, just the anti-glare properties.

Is sapphire worth the extra cost?
For daily wear, absolutely. A sapphire crystal will look new for years. For occasional wear, mineral crystal is perfectly fine.

Browse Funny Items Watches

• Sub Diver Watches — Mineral and sapphire crystal options
• GMT Watches — Sapphire crystal on premium models
• Dress Watches — Domed and flat crystal options
• Vintage Bronze Watches — Vintage-style domed crystals