Sapphire Crystal
Sapphire crystal is the transparent cover over the dial made from synthetic sapphire. It rates a 9 on the Mohs hardness scale, second only to diamond, so it resists scratches far better than mineral glass, although it costs more to produce.
At a glance
- Material
- Synthetic (lab-grown) sapphire
- Mohs hardness
- 9, second only to diamond
- Watch out for
- Glare in light if the crystal has no coating
The only thing standing between a watch dial and the outside world is the transparent crystal that sits over it. What that crystal is made of decides how the watch will look after years of wear. Sapphire crystal is synthetic sapphire grown in a lab, not the natural gemstone.
Why it holds up so well
Hardness measures how easily a material scratches. Sapphire rates a 9 on the Mohs scale, ranking behind only diamond on that list.
- Scratch resistance: everyday contact, keys, or a desk edge will not leave a mark
- Cost: that hardness comes at a price, as sapphire crystal costs more than mineral glass
- Glare: uncoated sapphire can throw glare in direct light, which most makers reduce with an anti-reflective coating
Where you will encounter it
Sapphire is the crystal of choice on watches that take water and knocks, such as a dive watch, where it pairs with the bezel and case to form a long-lived whole. You can explore the other external pieces in the parts section.
To see how it holds up in real use, read our guide to the best dive watches under £500.
Examples
The Orient Kamasu uses sapphire crystal, which makes it safer against scratches in daily wear.
View this watchThe Orient Mako, from the same family, carries a mineral crystal, a useful side-by-side for seeing the sapphire-versus-mineral difference at first hand.
View this watch
Comparison
The crystal types you meet most on a watch are sapphire, mineral glass, and acrylic. The core difference comes down to hardness and cost.
| Option A | Option B | Notes |
|---|---|---|
| Sapphire crystal | Mineral glass | Sapphire is far more scratch resistant at Mohs 9 but costs more, whereas mineral glass is cheaper yet scratches over time. |
| Sapphire crystal | Acrylic | Acrylic is soft and scratches easily, but those scratches can be polished out, whereas sapphire will not scratch but cannot be polished. |
Related terms
Watches that show this
Frequently asked questions
Can sapphire crystal scratch?
In practice it almost never does. Sapphire rates a 9 on the Mohs scale, behind only diamond in hardness, so everyday contact like keys or a desk edge leaves no mark. That is its main advantage over mineral glass.
What is the difference between sapphire and mineral crystal?
Sapphire is much harder and more scratch resistant but costs more. Mineral glass is cheaper and helps makers keep the price down, but it scratches over time. Within one family, the Orient Kamasu uses sapphire while the Orient Mako uses mineral.
Why does sapphire crystal show glare?
Uncoated sapphire can throw glare and reflections in direct light, which makes the dial harder to read. Most makers reduce this by applying an anti-reflective coating to the inside or outside of the crystal, so the dial reads more clearly.