There are a number of hardness scales used in modern science. The Moh's hardness scale measures the ability of one sample to scratch another. This is still often used to identify minerals especially by amateurs. Moh's suffers from some some inadequacies, for example one crystal face may be harder than another in a given sample. Metals such as potassium are more often rated on other scales, for example Rockwell or Brinell hardness tests which measure the ability of a diamond point to indent the sample. The Wikipedia page for Potassium gives the moh's hardness as 0.4 however.
Diatomite has a hardness of around 5.5 on the Mohs scale of hardness.
The mineral hardness scale is called the Mohs scale of mineral hardness, named after German geologist Friedrich Mohs who created it in 1812.
Azurite has a hardness of 3.5 to 4 on the Mohs hardness scale.
Flint has a hardness of 7 on the Mohs scale of hardness.
Dolomite has a hardness of 3.5 to 4 on the Mohs hardness scale.
Diatomite has a hardness of around 5.5 on the Mohs scale of hardness.
The mineral hardness scale is called the Mohs scale of mineral hardness, named after German geologist Friedrich Mohs who created it in 1812.
Limonite has a hardness of about 4 to 5.5 on the Mohs hardness scale.
Azurite has a hardness of 3.5 to 4 on the Mohs hardness scale.
Flint has a hardness of 7 on the Mohs scale of hardness.
The hardness is 3-4 on Mohs scale.
Nickel has a hardness of 4 on the Mohs scale.
Dolomite has a hardness of 3.5 to 4 on the Mohs hardness scale.
The Mohs scale is used to determine the relative hardness of minerals.
Aluminum Oxide is roughly 8.5 - 9.0 on the hardness scale.
Friedrich Mohs' hardness scale is simply known as the Mohs Scale of Mineral Hardness.
Granite is not assigned a number on the Mohs scale of hardness. The Mohs scale is a measurement of the relative hardness of minerals. Because granite is a rock composed of a variety of minerals, only the individual minerals which compose it have a Mohs hardness.