Sapphire vs Mineral vs Acrylic

The little disc of glass above your dial does more work than you'd think. It needs to resist scratches, survive impact, stay clear in heat, and (ideally) be cheap to replace.

The three contenders

Sapphire

• Hardness: 9 on the Mohs scale.
• Pros: virtually scratch-proof, hard-coatings stay clear for years.
• Cons: can shatter on hard impact, expensive to replace.

Mineral

• Hardness: 5–6.
• Pros: cheap, flexible, less likely to crack.
• Cons: scratches with day-to-day use.

Acrylic (Plexi)

• Hardness: 3.
• Pros: can be polished at home, warm vintage look, very impact-resistant.
• Cons: scratches if you look at it wrong.

So which is best?

• Daily luxury wear: Sapphire, every time.
• Beater or sports watch: Mineral or hardlex.
• Vintage repro or homage: Acrylic for the dome.