Scratch: How do you Determine the Hardness of a Mineral? (page 2)
- The hardnesses of a few everyday objects are as follows: Make and display a chart of the Mohs' scale, similar to the one shown. On the left side of the chart, list the names of the ten minerals used for each hardness of the Mohs' scale next to their hardness number. On the right side, list the everyday objects next to their hardness number. If you like, make simple sketches or tape or glue samples of the everyday objects next to the scale. Also include the pencils and gypsum or chalk from the previous experiments and their estimated hardnesses.
- Collect or purchase minerals to represent as many different hardnesses as possible. Using the everyday objects shown on your chart, evaluate the hardness of each mineral in your collection. Rub a sharp edge of the object whose hardness is known over the mineral to be tested. Determine whether the mineral or the object has been scratched. Estimate the hardness of the mineral. For example, if you can scratch the mineral with a paper clip but not with a copper coin, its hardness is between 3 and 4. A hardness of 4 would be a good estimate.
Display the mineral samples in order of their hardness. Use your hardness scale as part of the display. See chapter 20, "Collection," for suggestions on displaying a mineral collection.
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