This is slightly off-topic when it comes to photography, but I though it was worth mentioning.
In response to the artificial sapphire used by Apple in its Touch ID sensor, Corning is working to increase the scratch resistance of its Gorilla Glass.
While artificial sapphire is harder than glass (making it virtually scratch-proof) production costs and other concerns have prevented its use in electronic device screens. Glass costs far less to produce and can be given shatter-resistance and scratch-resistance properties depending on how it is produced. This gives Corning an advantage over artificial sapphire if it can create a glass that is strong enough and resistant enough to scratching to make sapphire pointless.
The challenge for Corning has to do with the physical properties of glass, including its natural hardness rating.
Glass typically has a hardness between 6 and 7 on the Mohs scale. Quartz particles are one of the main components of dust and it has a hardness of 7. For a material to be scratch-resistance, it needs to exceed the hardness of quarts. This means achieving a hardness over 7.
Silica when melted does not crystallize when melted and then cooled to form glass. Glass is sometimes referred to as a super-cooled liquid instead of a solid. There are also other materials added to the silica that can alter the properties of the glass. This additives are used to produce desirable properties in the end product, but can negatively effect the glass's hardness.
Corning can take a couple of approaches when attempting to produce scratch-resistant glass.
The first involves finding additives that increase the hardness of the finished product. (Similar to how adding carbon to iron produces steel.)
The second approach would be to apply a scratch-resistant coating to the exposed glass. A thin layer of aluminum oxide comes to mind.
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