Sapphire crystal is roughly ten times more scratch-resistant than mineral glass: it is the part that decides whether your watch still looks good in five years. It is also the detail manufacturers cut first when they want to lower the sticker price.
The cheapest. It scratches so easily that it marks in a pocket, but it has one advantage: scratches polish out with a paste. It is found on vintage watches and at the very bottom of the range.
Tempered glass, around 5 on the Mohs hardness scale. It is the standard on cheap watches. It takes small knocks, but it scratches on contact with sand, a key or a door frame, and the scratches are permanent.
Corundum crystallised in a laboratory, hardness 9 out of 10, just behind diamond. In everyday life, almost nothing scratches it: not keys, not concrete, not a car door. Its only weakness is that it is more brittle than mineral glass in a violent frontal impact. It is the glass used on every Modora watch.
A movement can be repaired, a bracelet replaced, a case repolished. The glass, however, is what you look at fifty times a day. A watch with a scratched glass looks worn out even if it runs perfectly. On a tight budget, a watch with a decent movement and sapphire crystal will age better than one with a more prestigious movement but mineral glass.
Bare sapphire reflects light slightly more than mineral glass. An anti-reflective coating, applied on the inner face or on both faces, removes most of those reflections and gives the impression that the dial floats with no glass above it. That is what separates a watch that is pleasant to read in full sun from one where you have to turn your wrist to see the time.
It needs nothing special. A microfibre cloth, slightly damp if needed, is enough. Avoid abrasive products and ammonia-based glass cleaners, which do not attack sapphire but can reach the seals and the anti-reflective coating. If your sapphire does end up scratched, it met something very hard, like sandpaper or a sharpening stone: a watchmaker will replace it, and the operation stays inexpensive.
Yes, in a violent direct impact on the glass, for example falling onto a concrete edge. It is highly scratch-resistant but more brittle than mineral glass, which absorbs impacts better.
No, chemically it is the same material. Synthetic sapphire is even purer and perfectly transparent, which the natural stone is not.
Yes, across the whole catalogue, including the models under 250 francs. It was a decision from the start: we would rather save on advertising than on the glass.
To understand the other key part of an affordable watch, read our guide on the Seiko NH35 movement.