The Mohs scale uses a "can you scratch me?" test to determine the relative hardness of materials, with diamond at 10 being able to scratch anything else. Any material higher on the Mohs scale can scratch one with a lower score.

The steel used to make kitchen knives is 5-6 on the Mohs scale while the Kadapa granite on your countertop is 7, so if you use expensive knives, use a wooden cutting board because granite will scratch steel.

The glass used in your smartphone screen is supposed to be 6, so technically a screwdriver made of steel should not be able to scratch it.

Fun fact: Apparently the Mohs scale is used typically for minerals while the Janka scale is used for wood - it is based on the amount of force required to embed half of a steel ball into the wood, and the Australian Bull-oak at 22,500 newtons is the hardest wood in the world