Practice using the Mohs hardness scale to rank minerals, interpret scratch tests, and estimate unknown mineral hardness.
Use the Mohs hardness scale as a reference: 1 talc, 2 gypsum, 3 calcite, 4 fluorite, 5 apatite, 6 orthoclase feldspar, 7 quartz, 8 topaz, 9 corundum, 10 diamond. Read each problem carefully and explain your reasoning.
Using scratch tests to compare mineral hardness
Earth Science - Grade 9-12
- 1
Rank these minerals from softest to hardest: quartz, talc, fluorite, diamond, calcite.
- 2
A mineral scratches calcite but does not scratch fluorite. What is the likely hardness range of the mineral?
- 3
A student tests an unknown mineral. It is scratched by a copper penny, but it scratches a fingernail. A fingernail has hardness about 2.5 and a copper penny has hardness about 3. What is the best estimate for the mineral's hardness?
- 4
Explain why diamond can scratch quartz, but quartz cannot scratch diamond.
- 5
A mineral sample scratches apatite and is scratched by quartz. What can you conclude about its hardness?
- 6
A mineral can scratch glass but cannot scratch quartz. Glass has a hardness of about 5.5 and quartz has a hardness of 7. What is the likely hardness range of the mineral?
- 7
Two minerals are tested against each other. Mineral A scratches mineral B, but mineral B does not scratch mineral A. Which mineral is harder, and how do you know?
- 8
A mineral has a Mohs hardness of 6. Name one reference mineral it should scratch and one reference mineral that should scratch it.
- 9
A geologist finds that an unknown mineral scratches gypsum, calcite, and fluorite, but does not scratch apatite. What is the best estimate of the mineral's Mohs hardness?
- 10
Why is the Mohs hardness scale considered a relative scale rather than a scale with equal-sized intervals?
- 11
A mineral scratches orthoclase feldspar but is scratched by topaz. Orthoclase feldspar has hardness 6 and topaz has hardness 8. Which Mohs reference mineral has a hardness between those two values?
- 12
A student claims, 'A mineral with hardness 8 is twice as hard as a mineral with hardness 4.' Explain why this statement is not correct.