Anti-reflective Sapphire Glass

First of all, sapphire crystal is more reflective than mineral crystal due to its higher index of refraction. (1,8 compared to 1,47). Applying one ore more layers of AR coating will limit this reflection to a very low level. Sapphire is extremely scratch resistant and this kind of crystal will look like new for years. The major drawback of mineral crystals is that they scratch much easier than sapphire crystals. Some say they also look “cheaper” in the way they reflect light.
A further distinguishing characteristic of sapphire vs mineral is how the droplet behaves if the watch is tilted off the horizontal. On the mineral glass the droplet will cling and elongate as it starts to drip, leaving a streak. On the sapphire, the droplet remains a ball shape. You can tilt the watch and rotate it and the droplet looks like a little clear ball rolling around on the surface of the crystal.