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I think it all depends on how it is hit or scratched.
I have both and the sapphire has a small scratch and the hardlex has a pin hole size ding.

There is alot of info out there on this debate.

I would not halter on either, so don't let it make you not buy a specific watch.
 

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From what I have heard:

Sapphire crystal is expensive (especially the thicker it is), but it is not impact resistant. It is HIGHLY scratch resistant, not scratchproof.

On the other hand, mineral crystal, even Hardlex, is very impact resistant, but less scratch resistant. Ideally, a thick curved sapphire crystal is best, but SO expensive. I'd settle for a thick curved minearl crystal.


Angelis
 

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The second link Ken posted above really goes a long way toward explaining the differences and dispelling the myths surrounding sapphire crystals versus hardened mineral crystals. Read it and if you still have any questions we'll be glad to help answer them.
 

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The most critical info from the second link, IMHO, as quoted from this link: http://www.larrybiggs.net/scwf/index...&id=1176221491

A LITTLE INFO. ON WATCH CRYSTALS:

There are four main types of crystals that concern us here: Sapphire, Seiko Proprietary, Acrylic & glass.

Artificial sapphire (as is used for watch crystals) is grown in a crystal lattice, unlike the flame-formed sapphire, like the kind you find in common graduation rings. The Sapphire crystals used in the overwhelming majority of watch crystals are artificially grown (in a boule. Once formed, the boule is then sliced and the pieces are then cut and polished to the desired shape. This material is very hard an resistant to scratches from common every day use, but it is also (like diamonds) brittle and has a tendency to shatter on impact (provided the impact is just right). Flame formed sapphire while chemically identical, lacks the internal crystalline structure and is much softer and brittle.

Hardlex is a Seiko proprietary type of hardened mineral crystal and comes in at least two different varieties (what goes in Seiko 5's is not the same quality of what goes into ISO divers). Hardlex is closer to 7 in the Moh's scale, but is much more flexible than sapphire. IOW's sapphire is harder but more brittle. Hardlex will scratch easier but resists impact much better. You can read more about Hardlex and the different types of it here:

http://www.larrybiggs.net/scwf/index.php?mod=103&action=0&id=1037842045

Sapphlex is also a Seiko proprietary type of hardened mineral crystal that is laminated (layered on the outer side of the crystal) with sapphire. The idea being to provide the best of both sapphires's superior scratch resistance and Hardlex's superior impact resistance.

The types of plastics used to make acrylic crystals has varied widely throughout the years. From a performance POV there are acrylics out there which perform very well in professional divers (most dive computers today use acrylic crystals). The problems with acrylics are that although they can be made to be very very impact and preasure resistant (at least in higher end ones), they are highly susceptible to scratches from simple bumps that would normally not scratch a simple mineral crystal. Provided the scratches are not too deep, they can generally be easily buffed out with the appropriate tools.

Buffing out scratches on mineral crystals (of any kind - sapphire included) is possible, but difficult and time consuming. even then if you are able to remove the scratch, you run the risk of altering the shape of the crystal in that spot. There are no real guaranties as to the quality of results. Although it is possible, it is usually not worth the time and effort to repolish a mineral crystal. Also, since replacements are generally inexpensive, most people prefer to just replace them.

Personally, I have no problem with Seiko's choice of high-end Hardlex (it is not the same stuff that goes on Seiko 5's), as it has superior impact performance to Sapphire and is not that drastically softer than sapphire (7+ on the Mohs scale vs 9 for sapphire).

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CRYSTAL SHAPES:

The overwhelming majority of mineral crystals (Sapphire, Hardlex, Sapphlex, or glass) come in of of two general shapes: flat or domed. There are tons of variations on the actual shapes of each from (and acrylics come in many more forms). There are pro's and con's to both general shapes.

Flat crystals tend to have a cleaner look and when used in tool watches such as divers, tend to be easier to protect, as they generally sit slightly lower than the bezel that surrounds them. The problems are that the flat shape makes them much more susceptible to impact failure (shattering and cracking), and the shape of the glass tends to act like a mirror when viewed at an angle - especially under water (this issue can be easily resolved with the use of AR coating, IMHO, preferably on the inside of the crystal).

Domed crystals, by their very nature distribute impact forces more evenly around the crystal and are thus more resistant to impact. Generally this characteristics tends to increase with the curvature of the dome. however, because of their raised profile dome crystals are far more susceptible to scratching, especially near the crystal's apex. the domed shape of the crystal naturally does away with the mirroring effect observed in flat crystals, but also distorts the image of the dial underneath it. Again the distortion is more pronounced the greater the curvature of the crystal. AR coating can be applied to domed crystals, but many would argue that it is not really necessary.
 

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The most critical info from the second link, IMHO, as quoted from this link: http://www.larrybiggs.net/scwf/index...&id=1176221491
:-d What did you leave out? (LOL) :-d

Thanks for reposting my article here. :-! I could have sworn that I also posted it to WUS when I originally wrote it. I'm pretty sure a copy of it is in the WUS archives either under the seiko forum or the dive watch forum (or both).
 

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I can't help it Isthmus---I saw it and I liked it, and felt that I'd save us all the trouble of searching the archives when we can all enjoy these bits of wisdom. I enjoyed the depth, and found that we both agree on the strong and weak points of both crystals.

However, does anyone still use acrylics? Can they be useful to us in these days?



Angelis
 

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Very good info! When I was having my Monster customized, I debated whether to get the Sapphire crystal or not. I decided not to as the Hardlex crystal still looks as good as the day I unboxed it. Good stuff that Hardlex.
 

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the hardlex is bada$$ - i have managed to get a couple of tiny tiny marks on the monster hardlex - but you cannot see them unless youre looking for them and a sapphire could have broken under the same impacts...perfect for a diver...
 

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I just want to personally thank Isthmus for the info he provided. I think that we can now all bring resolution to the question...


Thanks Isthmus---you are a font of information....:-!


Angelis
 

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To show how good Hardlex is, NASA specifies hardlex crystals for their Astronauts' Omega watches. It is less likely to shatter than is sapphire. Moreover, hardlex is very easily polished to 'good as new' by any competent watchmaker.
 

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That's good info RogerE. I have trusted Hardlex for some time now. The watch industry leans way more toward Sapphire crystal. A good thick curved sapphire crystal is very valuable these days.


Angelis
 

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That's good info RogerE. I have trusted Hardlex for some time now. The watch industry leans way more toward Sapphire crystal. A good thick curved sapphire crystal is very valuable these days.

Angelis
Sadly that is the watch industry preying on the fashionable but misinformed buying public. Much like how they advertise that watch movements are covered in "rubies" (or jewels). The truth is that there is NO jewelery value to either the rubies or the sapphire crystals, and they are both extremely cheap to manufacture in bulk. Jewlery stores have long sold watches (especially automatics with display backs or skeleton dials) by pushing the "jewels" and sapphire angle, as if it added any additional value to the watch (and often inflate their price accordingly). The uninformed public more concerned with the brand than the watch, simply buys the spiel, hook line and sinker.
 

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Sadly that is the watch industry preying on the fashionable but misinformed buying public. Much like how they advertise that watch movements are covered in "rubies" (or jewels). The truth is that there is NO jewelery value to either the rubies or the sapphire crystals, and they are both extremely cheap to manufacture in bulk. Jewlery stores have long sold watches (especially automatics with display backs or skeleton dials) by pushing the "jewels" and sapphire angle, as if it added any additional value to the watch (and often inflate their price accordingly). The uninformed public more concerned with the brand than the watch, simply buys the spiel, hook line and sinker.
If sapphire is not the best, then why does the Seiko MM600 Spring Drive have it. Surely, Seiko could of equipped the MM600 with Hardlex.
 
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If sapphire is not the best, then why does the Seiko MM600 Spring Drive have it. Surely, Seiko could of equipped the MM600 with Hardlex.
Let's put it this way.

Hardlex is the better compromise on a diver due to its combination of features. For one, it is less brittle than sapphire. One can of course engineer thicker sapphire crystals to compensate, but this comes at the expense of cost and case thickness, among other considerations.

Depending on the env. and usage, I will hesitate to call sapphire 'better' overall.

If one purchases a watch as jewelry or daily wear (e.g. desk diving), sapphire is obviously the better candidate.

To think about: Scratch-free crystal, yes. But what about the bezel? Esp. on divers.
 
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