MOHS Hardness Scale

MOHS Hardness Scale


The MOHS Hardness scale was created in 1812 by German mineralogist Friedrich Mohs and has been a valuable aid to identifying the hardness of minerals ever since. Fredrick Mohs based the scale on ten fairly common minerals of known hardness that were available at the time. Most ceramic tile manufacturers use the MOHS scale to test the scratch and abrasion resistance of the glaze that is applied to the tile. The MOHS scale is based on a relative value of 1-10; with 1 being the softest and 10 being the hardest. The following are the ten standard minerals used in the scale.

Some Ceramic Tile and Porcelain Tile manufacturers use this scale to test the hardness of the glaze and or body of the Tile.


MOHS Hardness Mineral Comparison to Other Flooring Materials
1 Talc Sheet Vinyl (inexpensive type)
2 Gypsum Wood Flooring (same hardness of a finger nail)
3 Calcite Laminate Floor (same hardness of a penny)
4 Fluorite Black Marble (not recommended for floor use)
5 Apatite Ceramic Tile (same hardness of a knife blade)
6 Feldspar Glazed Ceramic Tile (same hardness of window glass)
7 Quartz Glazed Ceramic Tile (same hardness as some granites)
8 Topaz Unglazed Porcelain (same hardness as most granites)
9 Corundum Unglazed Porcelain (same hardness as a ruby)
10 Diamond Diamond (No flooring this hard yet!)

The MOHS scale is strictly a relative scale, but that's all that anyone needs. In terms of absolute hardness, diamond (hardness 10 in the MOHS scale) actually is 4 times harder than corundum (hardness 9 in the MOHS scale) and 6 times harder than topaz (hardness 8 in the MOHS scale), because it isn't made for that kind of precision. The MOHS scale uses half-numbers for in-between whole numbers. For Example, dolomite, which scratches calcite but not fluorite, has a MOHS hardness of 3 or 3.5.

Below are examples of a few handy objects that also fit in this scale.

MOHS Hardness Mineral
2.5 Fingernail
2.5 3 Gold, Silver
3 Copper penny
4 - 4.5 Platinum
4 - 5 Iron
5.5 Knife blade
6 - 7 Glass
6.5 Iron pyrite
7+ Hardened steel file

The MOHS Scale is based on the fact that a harder material will scratch a softer one. By using a simple scratch test with some common household items, you can determine the relative hardness of the glaze on the tile.

For example:

Your fingernail has a hardness of 2.5. If you can scratch the glaze of the tile with it, you will immediately know that its hardness is less than 2.5. In other words, it is slightly harder than gypsum (Hardness of 2 on the MOHS scale) but softer than calcite (Hardness of 3 on the MOHS scale).

A penny
has a hardness of 3.0, which is slightly harder than your fingernail. So, if you can't scratch the glaze of the tile with your fingernail (Hardness of 2.5 on the MOHS scale), but you can scratch the glaze with a penny, you immediately know that it is at least as hard as calcite (Hardness of 3 on the MOHS scale).

The steel blade
of the average knife usually has a hardness of about 5.5. If a penny does not scratch the glaze of the tile but the knife blade does, then you can correctly conclude that it is harder than calcite (Hardness of 3 on the MOHS scale) but softer than feldspar (Hardness of 6 on the MOHS scale).

These are just a few examples, but as you can see by using simple household items and comparing them to the scale, you can get an idea of the hardness of your tile.

I hope this information gives you a better understanding and enough knowledge to help you test the hardness of the tile yourself, so you can select the right tile for the particular application in which the tile will be used