Anyone who has a smartphone is familiar with Gorilla Glass.  Gorilla glass is used on smartphones screens to protect them from cracking when they are dropped.  It is constantly getting stronger as newer versions are released and Gorilla Glass 4 will be the strongest yet.  To test the hardness, the glass has undergone new drop tests.  One test used 180-grit sandpaper to test against rough surfaces.  Another test dropped the glass from 3.3 feet high.  These tests are helping Gorilla Glass constantly improve.