What Does it Take to Scratch/Knick Modern Rolex Sapphire Crystal?

[Marantz2270]

I'm asking this largely to quell the OCD I feel about a new Sub I have acquired in the last couple months. I've knocked the watch against doorways and computer surfaces without any concern. But...I just knocked my crystal against the glass of my iPhone, and this was the only thing I thought might be hard enough to scratch the crystal (being that it is hardened glass). I don't see anything from my painstaking appraisal of the crystal condition thus far, but just curious if anyone has had issues knocking the crystal against other hardened glass? Is the sapphire likely significantly harder than iPhone glass?

I know a handful of questions get asked on this forum that are considered silly and illicit some sarcastic responses. Maybe that's what I deserve for asking about this. I really adore the watch and just want to be a good steward of it, so thank you in advance for your patience in considering my inquiry.