Crystal
The transparent cover over a watch dial, commonly made from sapphire, mineral glass or acrylic.
Also known as: watch glass, watch crystal, glass
Definition
The crystal is the transparent cover over the dial. It protects the hands and dial while allowing the time to be read, and it forms part of the case's environmental seal. Modern crystals are commonly synthetic sapphire, mineral glass or acrylic, each with different resistance to scratching, impact and polishing. Crystals can be flat, domed or highly curved and may carry anti-reflective coatings, magnifying lenses or specialised treatments. Despite the traditional name, a watch 'crystal' is not necessarily crystalline material—acrylic crystals are plastic.
Why it matters
Crystal material strongly affects everyday ownership. Sapphire resists scratches exceptionally well, acrylic can often be polished after scratching, and mineral glass sits between them in cost and properties. Shape and coatings also influence reflections and legibility.