stdragon :
But again, short of lamination, you can't have both maximum hardness and toughness. The closest to that is Diamond; and I'm not sure we're going to see CVD (chemical vapor deposition) of synthetic diamond mass-produced anytime soon.
Well if we're going to get that nitpicky, diamond is a crystalline structure, and vulnerable to fast fracture mechanics. A crack ends up concentrating stresses at the endpoint of the crack, causing the crack to to grow by "unzipping". That's why you can cut diamonds by hitting them with a chisel at certain angles.
Glass as we all know is also extremely vulnerable to fast fracture. Plastics are too (why it's easy to tear shrink wrap once you've cut a small notch in it), but less so than glass. Metals (whose grains slide, then interlock) tend to resist it well. As do fiber-reinforced composites like fiberglass and pykrete (combination of ice and sawdust). The substrate (resin or ice) experiences fast fracture, but the fracture eventually hits the reinforcing material (glass fibers or sawdust), which halts the "unzipping" process.
If so, we'd already have Apple's sapphire glass they'd sunk so much money into already.
It's not Apple's. It's corundum (aluminum oxide) crystals grown to sufficient size and thickness to be used as glass. Researchers figured out how to grow artificial corundum crystals (adding slight impurities turns them red or blue - which we call rubies and sapphires) back in the 1990s. The company making the corundum glass commercially had been producing them as bullet-resistant windshields for the U.S. military before Apple pulled their bait and switch on them. The technology existed and was developed long before Apple ever got involved. Heck, the aluminum foil in your kitchen drawer has a natural layer of corundum on it stopping it from oxidizing further.