I am now a 4th year BS Mining Engineering student and ever since my freshmen days, the first and most memorable lesson I won't ever forget is the Mohs' Hardness Scale and I would like to impart my knowledge on the said matter to all of you guys!!

Mining engineering is a branch of engineering that applies science and technology to the mineral extraction from the earth. It is also associated with other disciplines like geology, mineral processing, and metallurgy, geotechnical engineering and surveying. As a mining engineer one must already know about the Mohs' Hardness Scale.

Hardness is one of mineral's property which can be measured by the resistance to abrasion. The degree of abrasion is determined through comparison on which mineral is scratched by another. It plays a major role in identifying a mineral which can make the identification process much simpler and faster. For example, when mineral A is scratched to another mineral which is mineral B. If mineral B scratches mineral A, and mineral A does not scratch B then mineral B is harder than mineral A. And when they both scratch each other, then they are both of the same hardness.

Hardness can be much more understood using a scale devised in 1822 by an Austrian mineralogist Friedrich Mohs. This scale is based on the ability of a mineral to scratch another. The 10 minerals are placed in order from Talc being the softest and Diamond being the hardest. Each mineral in the scale scratches the mineral below it, e.g. the mineral Corundum can scratch the mineral below it which is Topaz but it cannot scratch the mineral above it which is Diamond.

Testing the hardness is done by scratching one mineral to the other. For a more accurate result, a sharp edge should be scratched against a smooth surface. After scratching, a permanent indention is left behind. Powder of the softer material becomes a product of the abrasion which would cover the area and should be brushed off to see whether the material actually scratched. Minerals of the same hardness if oftentimes hard to identify which of them (if not both of them) got scratched.

The scale only uses the relative hardness on each mineral. When you have a mineral specimen, which cannot be scratched by Apatite but can be scratched by Quartz, then it has a hardness of (5-7) on the Mohs' Scale.

There are common household items that can be used to determine the hardness of a mineral. The hardness of a Floor Tile which is (6.5), means that it can scratch Orthoclase and the minerals below it but cannot scratch Quartz and the minerals above. When you have a mineral specimen, you can first check it's hardness using your nail (with a hardness of 2.5). If you can scratch the mineral, then the specimen could be of the same hardness as either Gypsum or Talc and it can be stated that the mineral has a hardness of (1-2.5); if your nail cannot scratch the specimen, then it has a hardness of 3 and/or above. If the specimen cannot be scratched by your nail but can be scratched by a Floor Tile (and mineral A cannot scratch the Floor Tile), then mineral A has a hardness of (2.5-6).

Using a "testing kit" which uses the actual minerals, gives a better and more accurate range than the common household items. On the other hand, minerals might be damaged and could lose its value if not used (scratched) properly. It is preferable that the mineral inside the kit to be scratched over the specimen. If absolutely needed, one should scratch the specimen on the area of the mineral where the damage will be less noticeable.

If the mineral and the specimen can scratch each other, it is not safe to assume that the specimen is of the same type of mineral as the mineral on the scale. They are just of the same hardness, and nothing more.

Diamond is the hardest known natural material on Earth. However, it doesn't mean that it isn't brittle. As stated above, hardness only measures the ability of a material to be scratched and according to the Mohs' Hardness Scale diamond can only scratch itself. Diamonds of even the rarest colors does not affect it's hardness though. It will still scratch the same way as a white diamond does.