Gorrilla glass.is manufactured through immersion in a molten alkaline salt bath using ion exchange to produce compressive residual stress at the surface. This prevents cracks from propagating - for a crack to start, it will first have to overcome this compressive stress...
Above **** means---if something is tough that doesn't meant it won't bear a scratch,these glasses are designed to bear intense instant as well as gradual compressive stresses whereas scratching means to apply shear stress and molecular arrangement in both cases acts differently,for example imagine lots of sand in a 4mx4m box and now put onto it a column of 3mx3m,it will stand there and perhaps bear some load to(compressive),however if you apply shear force then it will simply erode the layer of sand below it...Gorilla Glass 2,The new manufactured glass is better able to resist the deep scratches that cause glass to break and is more flexible.....so "deep" here refers to a stress which is more on compression side than shear......hope I helped....
Structural Engineer here