Mohs Hardness Tester HD-2

While
the Mohs' Hardness test  was developed originally for
testing minerals, the same concept can be applied
to industrial materials.  Use this kit for "scratch
testing" substances to determine their Hardness according
to the Mohs' Hardness scale, which ranges from 1 to 10,
where Diamond is the hardest at 10, while Talc is softest at 1.