Test to Determine Mohs Scratch Hardness
Test to Determine Mohs Scratch Hardness
The test is named after Friedrich Mohs, who developed the scale in 1812. The Mohs scale ranges from 1 to 10, with 1 being the softest and 10 being the hardest. The scale is based on the ability of one mineral to scratch another, with a higher-numbered mineral scratching a lower-numbered mineral.
To perform the Mohs scratch hardness test, the following steps are typically followed:
- Obtain a set of reference minerals with known Mohs hardness values. The most common minerals used are:
- Talc (Mohs hardness of 1)
- Gypsum (Mohs hardness of 2)
- Calcite (Mohs hardness of 3)
- Fluorite (Mohs hardness of 4)
- Apatite (Mohs hardness of 5)
- Orthoclase (Mohs hardness of 6)
- Quartz (Mohs hardness of 7)
- Topaz (Mohs hardness of 8)
- Corundum (Mohs hardness of 9)
- Diamond (Mohs hardness of 10)
- Place the material being tested on a flat surface.
- Using the reference minerals, try to scratch the material with the lowest-numbered mineral first, and continue with progressively harder minerals until a mineral is found that can scratch the material.
- Note the Mohs hardness of the mineral that scratches the material being tested. This indicates the relative hardness of the material, with higher numbers indicating greater hardness.
The Mohs scratch hardness test is a quick and easy way to determine the relative hardness of different materials. However, it does have some limitations, such as the fact that it only provides a qualitative measure of hardness, and does not take into account other properties such as toughness or brittleness.
