Hardness | GRHardnessTester.comUsing the scratch test and Mohs Hardness Scale, we can determine the hardness of objects.  According to Mohs hardness scale, if a mineral has a hardness number larger than 5.5 then it is considered a hard mineral.  If a mineral has a hardness number less than 5.5 then it is considered a soft mineral.  Hard minerals can scratch glass and cannot be scratched by a knife blade while soft minerals do not scratch glass and are able to be scratched by a knife blade.  Here are a few common objects along with their hardness number.

Streak plate – 6.5

Glass – 5.5

Wire (iron) nail – 4.5

Penny – 3.5

Fingernail – 2.5

 

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