Something Zac from JerryRigEverything says in nearly every YouTube Video. He is known for
literally destroying phones for a living with various durability tests. Refers to the Moh's Scale of Hardness, and how strong certain cell
phone glass is.
Most cell
phone glass scratches at a level 6 on the Moh's Scale of Hardness with more scratches being visible with a level 7 'pick'.
"
Glass is glass, and scratches at a level 6 with deeper grooves at a level 7".