Rockwell hardness

The element neon has no hardness on either moh's hardness scale or rockwell scale unless it is frozen. These scales measure only solids.

The Mohs scale of mineral hardness is named after Friedrich Mohs, who developed it.

The Rockwell scale of metal hardness is named after Hugh and Stanley Rockwell, who created the machine that measures it. Hugh and Stanley Rockwell aren't directly related to each other.

The Shore Durometer scale for measuring the hardness of elastomeric materials like rubber is named after Albert Shore, who invented the measuring device called the durometer.

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Diamond is the hardest natural mineral, raking at 10 on the Mohs scale of hardness. Thus, it is a standard.