When I first got into watches, I spent a lot of time staring at specs. Movements, water resistance, lug width — I tracked all of it. The crystal? I barely noticed it was listed.
Then I scratched my first mineral glass dial, trying to squeeze past a door. And I started paying attention.
The Three Types of Watch Crystal
Every watch has a crystal — the transparent cover over the dial. There are three materials the industry uses, each with different properties, trade-offs, and price implications.
Acrylic (also called Hesalite or Plexiglass)
The oldest of the three. Acrylic is essentially a hard plastic, sitting at around 3 on the Mohs hardness scale — the mineralogy measurement that ranks materials by scratch resistance. At that level, it scratches easily. Your keys will mark it. A rough surface will mark it. Almost anything harder than the crystal itself will mark it.
The upside: acrylic doesn’t shatter. It flexes on impact rather than cracking, which is why NASA demanded it on the Omega Speedmaster for the Apollo missions — in zero gravity, shattered crystal shards floating inside a spacecraft posed a genuine danger to crew and equipment. It’s also polishable, meaning scratches can be buffed out at home with a proper crystal polishing compound like PolyWatch. And it produces a distinctive, warm, slightly domed look that vintage watch enthusiasts actively seek out.
You’ll find acrylic on field watches, vintage reissues, and some Casio G-Shocks. The Omega Speedmaster Hesalite version famously still uses it for historical authenticity.
Mineral Glass
Mineral glass is standard hardened glass — more resistant to scratches than acrylic, sitting somewhere between 5 and 6 on the Mohs scale. Seiko’s proprietary version is called Hardlex, which applies additional tempering for slightly better scratch resistance and impact performance than standard mineral glass.
In practice, mineral glass handles everyday wear well. You won’t scratch it on a sleeve or a desk. But keys, sand, and harder materials will eventually mark it, and unlike acrylic, you can’t polish those scratches out at home. It’s more shatter-resistant than sapphire, though not to the degree acrylic is.
Mineral glass is the crystal you’ll find on the majority of entry-level watches — Seiko 5s, most G-Shocks, the SKX series, and many watches in the $100–$300 range. It’s a reasonable, honest choice at that price point.
Sapphire Crystal
Sapphire crystal is synthetic corundum — the same mineral family as natural sapphire — rated at 9 on the Mohs scale. Only a diamond (10) or a few other materials will scratch it under normal conditions. For practical purposes, daily life does not scratch sapphire. Concrete, keys, metal edges — sapphire shrugs them off.
The trade-off is brittleness. Sapphire is harder but more brittle than mineral glass or acrylic. A sharp direct impact — dropping the watch face-first onto tile, for instance — can crack or shatter it. In real-world wrist use, this rarely happens, but it’s worth knowing. Replacing a cracked sapphire crystal is also considerably more expensive than replacing mineral glass.
Most mid-range and premium watches use sapphire. Once you’re spending $300–$400+, you should expect it as standard — and increasingly, you’re getting it. Brands like Orient and Citizen now offer sapphire crystals under $300, and even Tissot — a Swiss manufacturer — includes it on models from around $350 upward.
Does It Actually Matter?
Honestly? More than most people think, but not always in the way they expect.
If you wear one watch daily and change the battery yourself, scratch marks on mineral glass accumulate faster than you’d expect. A year in, the difference between a scratched mineral crystal and an unmarked sapphire is immediately visible.
If you’re hard on watches — outdoor work, sport, anything involving impacts — acrylic or mineral glass may actually serve you better than sapphire, purely because they won’t crack on a bad hit.
The Mohs scale tells you scratch resistance. It tells you nothing about impact resistance. A 9 on Mohs doesn’t mean invincible — it means scratch-proof under normal conditions, not shatter-proof under abnormal ones.
The practical takeaway: if you’re spending under $200, don’t let the lack of sapphire be a dealbreaker. If you’re spending $300+, it should be on the spec sheet — and in 2026, more often than not, it is.
The crystal is a window. It’s worth knowing what kind of glass is in it.
Now I know exactly what kind of crystal I want over the dial when I do find the perfect one.
— Ethan
More ticks, more tales — Watchesfanboy.
