What can scratch sapphire crystal?

[johnswatch]

Surely just because something is harder than another does not mean it can't be scratched.?
Stone is harder than shoe leather and yet you'll still see steps in old buildings with depressions where people have walked.

[ecsub44]

Originally Posted by johnswatch

Surely just because something is harder than another does not mean it can't be scratched.?
Stone is harder than shoe leather and yet you'll still see steps in old buildings with depressions where people have walked.

Are you serious?

[impalass]

The hospital I worked in (built 1911) had terrazzo floors and marble steps worn down over years from foot steps.

When looking down a hallway lower areas could be seen like paths.
The marble steps had even more obvious wear from foot steps/shoe leather.

Over time flowing water wears down rock. Not strange at all when our sapphire crystals get marked or scratched.