Watch crystal

Parts

• Acrylic glass (plexiglass, hesalite glass): the most impact-resistant ("unbreakable"), and therefore used in dive watches and most military watches. Acrylic glass is the lowest cost of these materials, so it is used in practically all low-cost watches.
• Mineral crystal: a tempered glass.
• Sapphire-coated mineral crystal
• Synthetic sapphire crystal: the most scratch-resistant; it is difficult to cut and polish, causing watch crystals made of sapphire to be the most expensive.