How to test hardness of diamond?

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Hardness refers to the extent of the ability of a material to withstand indentation or injury. Simply put, it implies the ability of an object to resist scratches. Yes scratches, not large holes or cracks. And there is no better object to demonstrate hardness (resistibility to scratches) than the hardest of all known materials: the diamond.

Diamonds are made of carbon atoms that each have 4 electrons within them. These electrons bond with the electrons of another carbon atom and so on and so forth. This results into diamonds exhibiting their characteristic hardness.

The Mohs Hardness Test

Minerals such as diamonds are identified by measuring their hardness and the Mohs Hardness Test is chief among methods to identify minerals by way of testing hardness.

It observes the resistance level of the test mineral to scratches when it comes into contact with 10 predetermined minerals.

Seeing as varying samples of the same type of mineral demonstrate a similar level of hardness, this test is ideal for identifying minerals.

The 10 minerals used for the test are listed from softest (talc) to hardest (diamond):

Talc
Gypsum
Calcite
Fluorite
Apatite
Orthoclase
Quartz
Topaz
Corundum
Diamond

‘Scratch Test’ of a Diamond

As shown above, the listed minerals are used to test the hardness of diamonds. If a mineral can be scratched by another, then that other mineral is harder.

Keeping this in mind, it can be demonstrated that a diamond is the hardest of all by using every mineral on the Mohs Test.

READ Why use the Vickers hardness test?

If any of the minerals apart from a diamond, can scratch the diamond that is being tested, then that is not a diamond.

We can determine that it is not a diamond by the fact that diamonds have already been proven to be impossible to scratch by other minerals.

Testing the Hardness of the Diamond

First off, the unblemished surface of the diamond needs to be located and once that is done the diamond needs to be held firmly in place. From here on all the steps are identical for every mineral on the Mohs Scale.

Any one of the minerals should be chosen to test the hardness of the diamond. Whichever mineral is chosen, its point should be pressed firmly against the diamond’s surface and dragged.

Wipe away any powder that may have appeared and observe the diamond’s surface. A flawless diamond would exhibit a complete resistance to scratches from any mineral other than another diamond. Thereby, it shall prove the hardness of a diamond.