The scale that identifies minerals by their relative hardness is called the Mohs Hardness Scale.

Here's how it works:

* The scale lists 10 minerals, ranging from the softest (talc) to the hardest (diamond).

* Each mineral can scratch any mineral below it on the scale, but cannot scratch any mineral above it.

* By scratching an unknown mineral with a known mineral from the scale, you can determine its relative hardness.

This makes the Mohs Hardness Scale a very useful tool for geologists and mineral enthusiasts for identifying minerals.