what is slate on the hardness
Slate is a rock, so you won't find it listed on the Mohs Scale, because that scale of hardness applies to minerals. I'll go out on a limb though, and suggest that slate is probably around 2 to 3 or so, but this will be variable, depending on the quality of the slate, and degree of weathering, etc. Slate is a rock, so you won't find it listed on the Mohs Scale, because that scale of hardness applies to minerals.