The gorilla glass screens are actually plastic,
Gorilla glass is NOT plastic.
It is a regular high quality glass that is tempered in a molten salt.
Quote from Wikipedia:
During its manufacture, Gorilla Glass is toughened by ion exchange. The material is submersed in molten potassium salt at a temperature of approximately 400 degrees C (750 degrees F), whereby smaller sodium ions leave the glass to be replaced by larger potassium ions from the salt bath. The larger ions occupy more space and are pressed together when the glass cools, causing potassium ions to diffuse far into the surface, thereby creating a 'surface' layer of high compressive stress deep into the glass, a layer more resistant to damage from everyday use.