Moh's scale is useful for field identification of minerals. It's not really useful as an all-purpose predictor of durability. Pressure is a huge variable. In a

Moh's scale is useful for field identification of minerals. It's not really useful as an all-purpose predictor of durability. Pressure is a huge variable. In a typical Moh's test, there is very little: just a person rubbing two stones together by hand. But with enough pressure, liquid water (hardness: none) can cut steel. Lead can damage steel or quartz if fired out of a gun. Etc. And as others have mentioned, snow might have particles of other materials in it as well. But just to be clear: Moh's scale does not mean that pure ice could never abrade steel.