If you’ve considered using natural stone for any type of home improvement, you may have been surprised at how many different options there are. There are various stones, colors and surface textures from which you can choose your own unique selections. One of the other things that people discover when they start to research stone is that there is a hardness measurement scale that shows how strong or weak a stone is.

The scale is useful because it can help determine what kind of care and maintenance will be necessary for certain types of natural stone. The “weaker” or more porous the stone, the more important it is to maintain it regularly. Stronger stones need less long-term maintenance, however, no natural stone is maintenance free.

Hardness Measurement Scale (MOHS)
10-Diamond
9- Corundum
8 – Topaz
7-quartz
6 – Country Spar
5 – Apatite
4 – Fluorite
3 – Calcite
2 – Plaster
1 – Talc

First developed in the 19th century, the hardness scale measurement is a list of minerals. Stones are made up of various types of minerals and most have a “hardness” rating that is represented by the MOHS. Certain well-known and commonly used natural stones are made from the minerals on this list. For example, you can see how the MOH scale represents the strength of the two popular natural stones listed below.

  • granite – This is the strongest of all natural stones. It is made up of feldspar and quartz, so it would have an index of 6 or 7 on the hardness measurement scale. Being higher on the scale means the rock is less porous, therefore less likely to stain and chip. It needs less maintenance but needs to be cared for properly.
  • Marble – Marble is known for having a beautiful and traditional “old world” look. It is also said to appear “soft”, and is actually a softer stone. Marble is primarily made up of calcite, so it typically has a MOHS rating of 3. Since it is a more porous stone and generally comes in a limited number of lighter colors, there is a greater danger of the stone becoming tarnished. That is why it must be properly sealed.

Understanding the hardness scale measurement is helpful when looking for natural stones. Now, if you see a rock label that says “2.5 hardness,” you’ll understand what the number means. Here’s another interesting note: Stones with a lower MOHS rate cannot scratch stones with a higher rate than yours. And, being at the top of the list, diamonds cannot be scratched by another material.