Who is Moe and why does he have a scale? - 8 to 10

Jennifer Lince
Jul 14, 2022
2 min read

Mohs (pronounced Moes) is a scale, devised by the German mineralogist Friedrich Mohs in 1812, that ranges from 1-10 (where 1 is the softest and 10 is Diamond) in which gemstones are tested to see their hardness. I.e. Quartz has a Mohs hardness of 7.

How to use the scale and test for hardnesses

When Fredrick Mohs created the scale, he selected 10 different minerals on basis of their hardness and used these to calculate the hardness of other stones.

1 - Talc

2 - Gypsum

3 - Calcite

4 - Fluorite

5 - Apatite

6 - Orthoclase

7 - Quartz

8 - Topaz

9 - Corundum

10 - Diamond

But how is this used to determine hardness?

You need to do a comparison test between the mystery stone (We’ll call it stone X) and the other stones.

Specimen A scratches Stone X= Specimen A is harder than X

Specimen A does not scratch Stone X = Stone X is harder than Specimen A

If they don’t scratch each other then they are of roughly the same hardness , test it with another specimen 1 up or 1 down the scale.

If Specimen B scratches then the hardness of X is between A and B

Example

You have a piece of Mookaite Jasper that you would like to test the hardness of. For the purpose of this example, we know that Mookaite is a 6-7 on the Mohs scale. To test this, first, we would choose a stone that seems of a similar hardness from the list above (Orthoclase).

Test Orthoclase against the Mookaite - neither should be scratched.

Get the next stone up ( Quartz) - Quartz should scratch the Mookaite therefore Mookaite is between a 6 and a 7.

If the quartz didn’t scratch it, the apatite should have been scratched by the mookaite and you would go to the next one up.

Examples of stones and their hardness (not an extensive list)

Mohs Hardness of 8

Topaz -8

Alexandrite - 8 1/2

Chrysoberyll - 8 1/2

Holtite - 8 1/2

YAG (Yttrium Aluminium Garnet) 8 1/2

Zirconia - 8 1/2

Rhodizite - 8-8 1/2