This was posted on another forum by someone else... very good info:
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This thread question keeps popping up ...
THERE ARE "SAPPHIRE" crystals out there that are not exactly what they seem. You can spot them by they way they explode when scratched. They are not 100% Mineral Glass, but nor are they 100% Sapphire ...
Think about it, how does a SAPPHIRE crystal get scratched? The wholebenefit behind Sapphire is the 9 out of 10 Hardness rating, so when Sapphire scratches, there has to be a reason .... [physics: a thin hard coating will scratch due to the softer subsurface base]
The CONCEPT
SAPPHIRE, (ALL SAPPHIRE IS MAN MADE when it comes to CRYSTALS) is not EASY to dome, but Mineral Glass is and it's heaps cheaper to process it this way. )
SO, you process a quick and easy MINERAL dome CORE and then .... DLC coat it with a SAPPHIRE outer layer ... COOL, you get a cheap Crystal that looks and feels in all respects SAPPHIRE!
Downside:
The coating appears to put a huge amount of stress on the core material. Think of the analogy of a balloon skin blown up. If the thin coat Sapphire is compromised, ( gets scratched, chipped ) these stresses which appear to be dynamic with eventually cause a catastrophic failure and the crystal shatters in result.
These are USUALLY marketed as "SYNTHIZED SAPPHIRE" which is an oxymoron as all Sapphire crystals are synthetic, so this marketing term means more than it implies. It means the Crystal is not 100% Sapphire, through and through.
DAVIDSEN Crystals are 100% Sapphire and AR coated. No cheap core, no shattering behaviour. The Quality and LOOK of them is far better than anything you will see out there as well. Your dial will look 10X better and you watch will visibly look better with the replacement crystal.
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