Fingernail (2. 5)[2] X Expert Source Sam Lagor, MScGeologist Expert Interview. 7 October 2021. Copper (3)[3] X Expert Source Sam Lagor, MScGeologist Expert Interview. 7 October 2021. Steel (5. 5)[4] X Expert Source Sam Lagor, MScGeologist Expert Interview. 7 October 2021. Quartz (7) Hardness
Write down your findings and continue the scratch test.
If you get a scratch with the copper but not with the fingernail, you know that the mineral has a hardness of at least 3 since that’s the hardness of the copper. If you’re unsure whether your mineral or the penny is harder, try scratching the penny with the mineral. If the mineral leaves a mark, the mineral is harder.
If it doesn’t leave a mark, the mineral must be below a 5. 5 hardness, which will help you narrow down the mineral when you interpret your results. You can also use a pocket knife or rock hammer for this part of the test. [10] X Expert Source Sam Lagor, MScGeologist Expert Interview. 7 October 2021.
If the quartz didn’t scratch your sample, your mineral is harder, which means it could be topaz, sapphire, or diamond.
For example, if both your fingernail and the penny were able to scratch the mineral, the penny is the harder object.
For example, if your fingernail and the penny were able to scratch the mineral but the steel nail couldn’t, your mineral can’t be harder than a 3.
If you’re trying to rub a limestone sample against a calcite sample or the copper penny, they might make faint scratches since they all have a hardness of 3, for instance.
For example, if the copper penny (3) didn’t scratch the mineral but a steel nail (5. 5) did, you know that the hardness is between these. You can safely estimate the hardness of your mineral to be 4, which might be fluorite.
