sapphire crystal types

An acrylic watch crystal is hardened plastic, which has the advantage of being resistant to shattering, but can be scratched fairly easily. Fortunately, scratches can be easily removed from acrylic.

A mineral glass watch crystal is hardened glass (Seiko name – Hardlex), which is much more scratch resistant than acrylic, but significantly less than sapphire.  Mineral crystals are also somewhat better at shatter resistance compared with sapphire.

A sapphire crystal is made of synthetic sapphire, which is a transparent form of corundum, or aluminum oxide (Al2O3). It is extremely hard (Moh’s scale 9 – Diamond is 10), and will resist scratching by most substances short of diamonds. Premium watches generally use sapphire crystal (e.g. Rolex Omega AP Panerai Bremont Hublot GP Cartier).

Crystaltimes produces 5 designs of sapphire crystal:

1. Flat (both sides)
2. Single Dome – Domed top surface flat underside.
3. Double Dome – Domed top and underside surfaces.
4. Bubble Dome – A high double domed bubble like design.
5. Top Hat - A flat vintage top hat style design.