MOHS Scale

The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.

Mohs based the scale on ten minerals that are all readily available. As the hardest known naturally occurring substance, diamond is at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material.

For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5.

On the Mohs scale, a pencil lead has a hardness of 1; a fingernail has hardness 2.5; a copper coin, about 3.5; a knife blade, 5.5; window glass, 5.5; steel file, 6.5.

As for tiles, the higher the Mohs hardness of the tile surface, the less the risk that objects and other other materials can scratch or etch it permanently.