Let us first start with what is a watch crystal? The crystal ("or glass") is the window to a watch. It is the part of the watch that takes a constant beating from daily use, yet is often overlooked.
So to better appreciate what a sapphire crystal is, let us touch on other types of glass.
This type of watch "glass" is not glass at all, it is plastic. It is cheap to make and common a material, therefore it is generally found on low-end watches. Since it is plastic it lends itself to being easily scratched or broken.
A step up from acrylic, mineral glass is made from tempered glass.
Tempered glass is semi scratch-resistant. It is also inexpensive to manufacture, which makes it a great candidate for watch glass. Not surprisingly at all, mineral crystals are the most common glass you find on a watch.
Finally, the highest tier of watch crystal is sapphire. By sapphire, we mean synthetic sapphire, which is created by superheating aluminum oxide. After the superheated aluminum oxide crystallizes into synthetic sapphire, it is cut into watch crystals by diamond-coated saws. It is not an overkill to use a diamond-coated saw, because that is the only way to cut synthetic sapphire. This is an expensive process, though it yields a crystal that can only be scratched by something as hard as a diamond.
Anti Reflective Coating
Sapphire watch crystals are more reflective than other types of watch crystals. Therefore they require an anti-reflective (AR) coating. Some watch manufacturers apply AR coating on both sides of the crystal. However, the AR coating can scratch, which makes it look like the sapphire crystal is scratched. Thereby defeating the purpose of the expensive sapphire crystal.
All TAAKT timepieces come with a sapphire crystal coated with an anti-reflective film on the inside of the crystal, ensuring long-life and use.