In 1822 a German scientist by the name of Frederick Mohs set up a scale to determine the approximate hardness of minerals. (SEE CHART ABOVE!!!) He arranged the minerals in his scale from softest (Talc) to hardest (Diamond). The minerals get increasingly harder as you read down the scale, but they do not increase in hardness at a constant rate. Example: Calcite is not twice as hard as talc and a diamond is not 10 times harder than talc. In fact a diamond is over 40 times harder than talc. The line graph above shows you this relationship.

This property like color is arbitrary because the hardness of a mineral varies slightly from one specimen to the next. We can determine the approximate hardness of a mineral by running a group of tests. Scratch the mineral in question with a fingernail, penny, iron nail, or glass slide. If the mineral shows a scratch mark from one of the testing materials the mineral is said to be less hard than the mineral that scratched it. Example: A piece of pink feldspar will not be scratched by a fingernail, penny, or an iron nail, but will be scratched by a glass slide. The feldspar is said to be harder than the first three testing materials but not as hard as the glass slide.

You can use the following materials to run your own mineral hardness tests. 1) bar soap 2) fingernail 3) penny 4) easy to scratch knife blade 5) hard to scratch a knife blade 6) will scratch glass slide 7) quartz crystal.

Click on the "Next" button to see how minerals break.