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Comment by Stedag | Hacker News Reader

It’s definitely price performant at 6.5 on the mohs scale, sapphire panels are 2-4x more expensive to produce but 9 on the mohs scales so they’re typically only found in watches I bet. At a 10 on the mohs scale diamond is still best for hardness. Maybe the same effect of the prince Rupert’s drop could be induced on a round diamond with an alpha particle beam treatment where you add these ions primarily on the surface of the stone.

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I'm not exactly a watch nerd, so don't know how true this is, but I hear that sapphire shatters on impact. Or maybe that's just an excuse for people peddling "alternative" materials for their watches?

But if it is true, then I'd say that sapphire is a poor choice for mobile phones. IME I'm far more likely to drop the phone, preferably on some form of hard surface, that to scratch it. Phones are nowadays so ridiculously big, that there's zero chance I'll have anything else in my pocket.

Diamonds also shatter. It's got roughly the same toughness as sapphire but the cleavage planes are more annoying (in that it has them, while sapphire doesn't).

I believe Apple tried to get sapphire for phones screens at some point, but their supplier folded.

They did however manage to get Sapphire on the watch display (at least on the stainless steel LTE edition of the apple watch series 4 and 8, which I'm aware of).

The difference between my watch (which was 4 years old at the time) and a colleagues almost brand new apple watch (without the sapphire) was really telling, is his was lightly scratched on the edges despite him being quite careful, and I was exceedingly reckless with mine as I considered it old- yet there was not a single defect.

That was a major reason for me to upgrade to the LTE of the next version of apple watch that I bought.

The sapphire on the Apple watch was a marketing gimmick, barely better than gorilla glass: https://www.youtube.com/watch?v=RF72hGIdrG8&t=10m20s

But there are other devices with better sapphire that actually live up to the hype.

Well, maybe.

I have now had watches for 10 years without issue and my phone displays seem to scratch.

I’m not doubting you’re correct, I never boight it for this reason, it was just an interesting retrospective observation. Clearly its working for me, and I’m not sure I have anything with gorilla glass.

Unless the Pixel 7 has it.

EDIT: My Pixel 7 does have gorilla glass indeed and it has two scratches on the display despite being extremely rarely used. (its my work phone and sits on my desk mostly)

I have a Series 5 with the Saphire glass but my clumsy ass dropped it in the kitchen onto a stone floor. The edge of the glass shattered and while I still use it to this day, it's an ugly reminder of my clumsiness. The repair offer from Apple was to get a new one with a very slight discount.

Long story short, it is more scratch resistant but also more prone to break. So be careful.

I wonder if they could put in tiny reaction wheel gyroscopes (to make it land in a safe orientation) or tiny linear reaction masses, or perhaps tiny replacable airbags or tiny sodium azide NaN3 charges/nozzles to blow air just before landing, to make for a gentler landing, replacable of course.

Tiny replacable airbags, on the corners. Preferably it should somehow detect the elasticity of the surface its falling to or going to hit.

There was a prototype design that a German student, Philip Frenzel, produced in 2018 that used the accelerometers to detect freefall and push out little spring claws to protect the device. It was supposed to be in production circa 2019 I think but I can't see evidence that it made it. YouTube has videos.

Thanks for the warning!

I suspect the edges are more at risk than the face, as I've struck the face very hard against the edge of a scaffolding pole and there was no damage - which, actually shocked me a lot based on the force.

From what I remember, it was mainly because it was a fair bit more expensive to manufacture.

The threat isn't so much scratching it in your pocket (but that is possible, I typically have my sunglass clip in the same pocket--it's supposed to be in it's own case but in theory something could happen) as scratching it against things.

also note that Mohs is a qualitative ranking rather than a linear scale. Huuuuuge difference in hardness at the top end.[0]

[0] https://geology.com/minerals/photos/mohs-vickers-comparison-...

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