Would glass wear faster than diamond or it doesn't matter what material it is? I am interested in how a hard material is abraded by a soft material like human skin. I know stone floors are rubbing off over the years, but on top of that there are various other factors, for example- pollution, chemical reactions (they're not as inert as diamonds or glass). If a diamond were to rub over a period of several hundred years, then how are very tiny diamonds found in alluvial deposits (and their age is estimated at millions of years)? What about glass that we use on a daily basis? We don't see how it wears out? Does using a glass every day mean that millions of quartz atoms end up in my body?