You are valid in pointing out that my use of the term “comparable” in the above post was subjective and not objective. It would have been more appropriate to have phrased things along the lines of Gorilla Glass being more comparable to sapphire in those respects than standard mineral glass, which was the intent.

As I’m sure you are also aware, the topic of material hardness itself is not altogether unambiguous, which is why so many different systems of attempting to classify hardness exist, such as Vicker’s, Rockwell, or the now outdated Mohs system. The fact that the Mohs system is no longer used in industry is more or less because the ability of one material to scratch another (“scratch resistance”) is not considered synonymous with hardness. Nor is strength synonymous with hardness.

Anecdotally, yes, it is possible for small particles of aluminum oxide on a sandy beach to scratch Gorilla Glass. Hardened steel can be as hard as 900 kgf/mm2 and could scratch it as well, but it would be very brittle steel. Most hardened steel is tempered well below that, to somewhere between 500 & 700 kgf/mm2 while mild steel is typically around 140 kgf/mm2.

In terms of strength, I would take Gorilla Glass over sapphire. In terms of scratch resistance, I’d take sapphire. For the case at hand, Gorilla Glass was a better fit and, for general use, its scratch resistance is comparable to what a client can expect from sapphire. Both will be scratched by diamond and both can be scratched by aluminum oxide. There is not a whole lot else out there that might commonly come into contact with the watch glass that could scratch it otherwise.

This simply isn’t true. Anyone who’s owned a smartphone and a watch will know it anecdotally, but you can back it up with numbers too. GG has a vickers hardness of at best 700 kgf/mm2. Saphire is 2300 kgf/mm2

http://www.corning.com/docs/specialtymaterials/pisheets/PI2317.pdf

http://americas.kyocera.com/kicc/pdf/Kyocera%20Sapphire.pdf

The crystal looks far better with it. In fact I have some cheap Seiko and a fashion watch that I had coated and it made the world of difference.

The only question that goes unanswered on Horology-Matters is the one I posed about what watchmakers want from a watchmaking organization. Not one idea has been given yet.

I appreciate your ideas, I read them, I think about them and they do help me formulate my ideas and views of the watchmaking profession. I do not believe that you are a member of AWCI so I will say no more to try and acquire your vote.