Sapphire was seldom used in watches in the past, but now most watches use sapphire glass. Sapphire watch glass does have great advantages, not easy to scratch and wear, because its hardness is grade 9, second only to diamond.
Sapphire glass can also be worn out. In the early years, radar watches advertised that their watches were "never worn", which was obviously exaggerated, and later changed to wear-resistant, which is almost the same. It is true that sapphire glass is only wear-resistant. Everything that is hard is often brittle. Therefore, sapphire glass is easy to break or burst under severe collision.
In addition, when something sharp scratches the glass surface, it is easy to cause scratches. This depends on the strength and speed of scratches. The sharper the contact point, the greater the speed and strength, the more vulnerable to scratches. There is also the glass force angle, about 45 degrees of force angle, relatively easy to cause larger scratches.