Crystal harder than Sapphire?

[corght]

Is there watches with a crystal harder than Sapphire? The only logical choice would be synthetic diamond. Is there any watch out there with a diamond crystal?

[zeFiF]

hi,

check this : Mohs scale of mineral hardness - Wikipedia, the free encyclopedia

[Wannaduck]

Can't get any better than Sapphire and Steel :)

[corght]

hi,

check this : Mohs scale of mineral hardness - Wikipedia, the free encyclopedia

Sapphire is a corundum, in the same family as Ruby. It's a crystalized aluminum oxide.

[workaholic_ro]

Disambiguation from the perspective of a mining engineer:
Although useful, the article is a little confusing and incomplete. And so is the host (Wikipedia), but we still love it (at least as long as it's free).
In pure crystalline form 1,3,4,5,7,8,9,10 are clear and colourless. Calcite and feldpar are exceptions, calcite is clear but with a slight yellow tint and feldspar translucent or opaque.
The colour is given by very small amounts of impurities, usually metals. Sometimes, these metals also change the name of the minerals and so we have the variations: amethyst for the violet quartz, sapphire for the green corundum (can be blue, black or yellow too) and ruby for the red sapphire. Diamonds makes no exception, but keeping the original name. BTW, the most common colour of topaz is yellow and not blue.
Colourless sapphire is rare as a natural gem, therefore what we are used to call sapphire crystal in our watches is actually glorified synthetic corundum glass :)

[WnS]

Transparent Silicon Carbide and Diamond are harder than Sapphire, and they can theoretically be used on watch crystals - probably too brittle and expensive for such a purpose though.

[corght]

Disambiguation from the perspective of a mining engineer:
what we are used to call sapphire crystal in our watches is actually glorified synthetic corundum glass :)

Thnaks for the scientific explaination. So Calcite and feldpar are not crystals?

[corght]

Transparent Silicon Carbide

Hmm.. Silicon Carbide... I will search this material, seems interesting. :)

[workaholic_ro]

Thnaks for the scientific explaination. So Calcite and feldpar are not crystals?

Mohs scale only applies to monomineralic crystalline forms. When I said exceptions I was talking about the colour.
No idea if there is any Moissanite (SiC) crystal of a size of a wristwatch, we need to investigate. But not the hardness is the subject to complain about sapphire, I don't think that scratches are very common. An unbreakable crystal rated with 9 on Mohs scale would be close to perfection.
BTW, just got an idea for a new thread :)

[corght]

It's true that a hard material is sometimes brittle. The goal is to find a good compromise between hardness and strenght.