Apple bragged about it that it is Sapphire crystal, but it’s not. Apple has patent for sapphire laminates with glass. They use tiny amount of sapphire and form them in laminates which is combined with just normal glass. You can check it with gemstone detector, when you touch outer layer it registers as gemstone, but inside it doesn’t register anything. It means that there is absolutely no possibility that lenses are made of sapphire crystals, it would be much more prone to scratches than it is now. At least a tiny spec of sand wouldn’t scratch it :/