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Although reference books and websites often list a single hardness for each mineral, many minerals have variable hardness. They have greater or lesser hardness depending upon the direction in which they are being scratched. A well-known example of a mineral with variable hardness is kyanite. Kyanite frequently occurs in blade-shaped crystals. These crystals have a…

Diamond is not the hardest substance known, but the materials that are harder are much more rare. Researchers have reported that wurtzite boron nitride and lonsdaleite can be harder than diamond. It is unlikely that you will find a mineral that is softer than talc. However, a few metals are softer. These include: cesium, rubidium,…

An alternative to using the reference minerals for testing is a set of “hardness picks.” These picks have sharp metal points that you can use for very accurate testing. The picks allow much more control, and their sharp points can be used to test small mineral grains in a rock. The sharp picks can be…

Some people make their own hardness testing kit using a few common objects. The contents of their kit often include:  their fingernail a copper coin a nail a piece of glass a knife blade a steel file a streak plate a piece of quartz This field hardness testing kit sounds like a great idea. These items cost very little, and you can…

“Hardness” is the resistance of a material to being scratched. The test is conducted by placing a sharp point of one specimen on an unmarked surface of another specimen and attempting to produce a scratch. Here are the four situations that you might observe when comparing the hardness of two specimens:   1. If Specimen…

Friedrich Mohs, a German mineralogist, discovered the hardness scale in 1812. He selected ten minerals of distinctly different hardness that ranged from a very soft mineral (talc) to a very hard mineral (diamond). With the exception of diamond, the minerals are all relatively common, easy to obtain, and inexpensive. See the accompanying table of the…

If you have a mineral specimen of unknown hardness, and reference mineral #5 can scratch it, then the hardness of your specimen is less than or equal to a Mohs hardness of 5. Similarly, if your specimen cannot be scratched by reference mineral #5, then its hardness is greater than or equal to a Mohs…

The Mohs Hardness Scale is a set of ten reference minerals (numbered 1 through 10) that are used to determine the relative hardness of minerals and other objects. In this test the hardness of a mineral is defined as its “resistance to being scratched”. A list of the Mohs Hardness Scale Minerals is shown in the table…