Pocket sand, putting your phone face down on any surface where sand might have been is enough for scratches.
It's all about hardness [1], ordinary iron / metal is quite soft (4 - 5) scale on mohs scale, while gorilla glass is at least a 7. It has nothing to do with how "sharp" an object is, paper will never scratch steel and regular keys will never scratch glass. Someone on XDA [2] made quite a passionate case about this.
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Pocket sand, putting your phone face down on any surface where sand might have been is enough for scratches.
It's all about hardness [1], ordinary iron / metal is quite soft (4 - 5) scale on mohs scale, while gorilla glass is at least a 7. It has nothing to do with how "sharp" an object is, paper will never scratch steel and regular keys will never scratch glass. Someone on XDA [2] made quite a passionate case about this.
[1]http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
[2] http://forum.xda-developers.com/galaxy-s2/general/misconcept...