If I can just say something here ... sapphire watch crystals are not dug up out of the ground, nor are there huge, perfect chunks of mined sapphire which are polished into watch crystals. Pure, clear MAN MADE sapphire is laboratory grown in lengths, in rod form up to 400mm in width, and cut to the required thickness. Watch crystals are not mined. Sapphire watch crystals are synthetic sapphire.
They are desirable due to their hardness .. 9x harder than glass.