What are sapphire crystals commonly used for in watches?

Sapphire crystals are widely recognized for their exceptional durability and scratch resistance, which makes them ideal for use as protective covers on watch faces. The hardness of sapphire, which is a synthetic corundum, is rated 9 on the Mohs scale, second only to diamond. This outstanding hardness ensures that the watch remains clear and free from scratches over time, maintaining the watch's aesthetic appeal and functionality.

Utilizing sapphire crystals not only protects the watch's dial from everyday wear and tear but also allows for a clear view of the watch's face, showcasing the design and any intricate details within the watch. This quality positions sapphire crystals as a premium choice for high-end watches where both durability and visual clarity are paramount.

In contrast, decorative pieces would not serve the functional purpose that sapphire crystals are known for, while internal mechanics and power sources refer to entirely different components of watch design and operation. Internal mechanisms involve gears and movements that keep time, and power sources refer to batteries or automatic winding systems, which are unrelated to the protective features of the watch crystal.