The Ion-X glass found on the Apple Watch Sport isn’t quite as tough as sapphire glass found on the more expensive Apple Watch models, but it holds its own.
Unbox Therapy posted a scratch test video in which the Ion-X glass was exposed to keys, a knife, steel wool and sandpaper. To its credit, the new glass type held up against everything but the sandpaper, albeit it was noted that the sapphire glass coating found on the iPhone 6 and 6 Plus handsets held up to the sandpaper during scratch tests.