Materials
The materials used in a watch crystal, case and strap: sapphire, mineral, steel, titanium and more.
What a watch is made of largely decides how it ages, how long it lasts and how it feels. The gap between a scratch-proof sapphire crystal and a mineral one that marks easily, or between light titanium and classic steel, shows up quickly in daily wear.
The terms in this section explain crystal, case and strap materials in plain language, so you understand where a watch's price and durability come from.
- Hardlex
- Hardlex is Seiko's branded hardened mineral crystal. It is tougher and more shatter resistant than ordinary mineral glass, yet softer than sapphire, so keys or grit can still scratch it. You will find it on the Seiko 5 and entry-level Prospex models.
- Mineral Crystal
- Mineral crystal is a hardened glass fitted over the watch dial. It is far cheaper than sapphire and more resistant to shattering on impact, yet it scratches more readily, rating around 5 on the Mohs hardness scale against sapphire's 9. Seiko's Hardlex is a branded mineral glass.
- 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.
- Stainless Steel
- Stainless steel is the standard metal for watch cases, usually the surgical-grade 316L alloy. It is corrosion resistant and strong, and it takes both a brushed and a polished finish. It is heavier than titanium and is the default for Orient, Seiko and Citizen cases.
- Titanium
- Titanium is a case metal much lighter than steel and hypoallergenic, with high strength. It resists corrosion well, but it scratches more readily than steel unless its surface has been hardened. Citizen uses titanium across many of its watches, which is why you meet it so often.