Sapphire vs Mineral Glass: What's the Difference?

When choosing a watch, most people focus on the dial, case size, or bracelet.

Yet one of the most important - and most misunderstood - elements sits directly on top of the dial:

The glass

Two terms appear frequently in watch specifications:

• Mineral Glass
  
  
• Sapphire Crystal

But what’s the real difference?

Let’s break it down properly.

What Is Mineral Glass?

Mineral glass is hardened, heat-treated glass designed specifically for watches.

Advantages

• Strong and impact-resistant
  

• More flexible than sapphire (less prone to shattering)
  

• Cost-effective
  

• Clear and perfectly suitable for everyday wear
  

Why It’s Widely Used

Mineral glass has been the industry standard for decades, as it offers excellent durability at an accessible price point.

For many wearers, mineral glass performs flawlessly for years.

What Is Sapphire Crystal?

Sapphire crystal is synthetic sapphire - not glass, but a lab-grown crystalline material.

Advantages

• Extremely scratch resistant
  

• Exceptional clarity
  

• Premium feel and finish
  

• Maintains pristine appearance over time
  

On the Mohs hardness scale:

• Mineral Glass ~5–6
  

• Sapphire Crystal ~9
  

(For reference, diamond = 10)

Scratch Resistance: The Key Difference

This is where sapphire truly separates itself.

• Mineral glass can pick up scratches from keys, desk edges, grit
  

• Sapphire crystal resists almost all daily contact marks
  

Over years of wear:

• Mineral - May show light surface wear
  

• Sapphire - Typically remains visually flawless

But Sapphire Isn’t Perfect Either

Important nuance - sapphire has one trade-off:

Brittleness

Because sapphire is so hard, it’s less flexible.

A sharp impact that mineral glass might survive could crack sapphire.

This is rare in normal use but worth understanding.

Which is best for me?

The honest answer: It depends on how you wear your watch.

Choose Mineral Glass If You:

• Want excellent durability at a more accessible price

• Wear your watch casually / rotationally

• Prefer impact tolerance

• Aren’t concerned about the occasional light scratch

Within the Rotary collection, we also use mineral glass for domed watches, giving a vintage high-glass look to the watch. This allows for everyday performance, balanced with vintage inspired charm.

Choose Sapphire Crystal If You:

• Wear your watch daily
• Want long-term cosmetic perfection
• Value premium finishing
• Tend to be hard on watches (diving, travel, active lifestyle)

This is why our Seamatic collection for example uses sapphire crystal - they are designed from the off to be hard wearing watches, engineered for reliability in tough environments.

Mineral glass is not “cheap” nor “bad.”

It remains:

• Reliable

• Durable

• Trusted for watchmaking

Sapphire crystal is simply a premium upgrade, not a necessity.

How Rotary Approaches Crystal Selection

At Rotary, crystal choice is guided by:

• Intended use
• Design positioning
• Case construction
• Overall value balance

Both are chosen deliberately - with each serving a particular purpose within our range.