Click image to open full size
Mohs hardness scale from 1 (softest) to 10 (hardest) Memory Aid Cheat Sheet
A printable reference covering Mohs hardness minerals, scratch testing, hardness ranks, and a memory aid for grades 9-12.
Related Worksheets
Related Infographics
Study as Flashcards
The Mohs hardness scale ranks common minerals from 1, the softest, to 10, the hardest. Students use this scale to identify minerals by testing which materials can scratch others. This cheat sheet helps students memorize the order and connect each number to a key mineral. It is useful for labs, mineral identification, and Earth science review. The core idea is that a harder mineral scratches a softer mineral, but a softer mineral cannot scratch a harder one. The standard Mohs scale is 1 talc, 2 gypsum, 3 calcite, 4 fluorite, 5 apatite, 6 orthoclase feldspar, 7 quartz, 8 topaz, 9 corundum, and 10 diamond. A common memory aid is The Girls Can Flirt And Other Queer Things Can Do, using the first letter of each mineral in order. Everyday objects such as a fingernail, copper penny, steel nail, and glass plate can help estimate hardness.
Key Facts
- The Mohs hardness scale ranks minerals from 1, talc, to 10, diamond, based on scratch resistance.
- The complete order is 1 talc, 2 gypsum, 3 calcite, 4 fluorite, 5 apatite, 6 orthoclase feldspar, 7 quartz, 8 topaz, 9 corundum, 10 diamond.
- A harder mineral can scratch a softer mineral, so quartz with hardness 7 can scratch calcite with hardness 3.
- A softer mineral cannot scratch a harder mineral, so fluorite with hardness 4 cannot scratch quartz with hardness 7.
- If two minerals have the same hardness, they may scratch each other weakly or leave a mark that is not a true scratch.
- A useful memory aid is The Girls Can Flirt And Other Queer Things Can Do, matching talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, diamond.
- Common test tools have approximate hardness values: fingernail 2.5, copper penny 3, steel nail about 5.5, glass plate about 5.5, and streak plate about 6.5.
- Mohs hardness is an ordinal scale, so diamond at 10 is not simply twice as hard as apatite at 5.
Vocabulary
- Mohs hardness scale
- A scale from 1 to 10 that ranks minerals by how well they resist being scratched.
- Scratch test
- A mineral identification test in which one material is used to see whether it can scratch another material.
- Talc
- The softest standard mineral on the Mohs scale, with a hardness of 1.
- Diamond
- The hardest standard mineral on the Mohs scale, with a hardness of 10.
- Relative hardness
- A comparison of how easily one material can scratch another material.
- Ordinal scale
- A scale that shows order or rank but does not show equal size gaps between each number.
Common Mistakes to Avoid
- Thinking the scale has equal intervals is wrong because Mohs hardness is ordinal, so the gap from 9 to 10 is not the same as the gap from 1 to 2.
- Confusing a powder mark with a scratch is wrong because a true scratch is a groove in the surface, not loose material rubbed onto it.
- Testing on a weathered or dirty surface is wrong because coatings, dust, or altered mineral surfaces can give a false hardness result.
- Forgetting that harder scratches softer is wrong because the direction matters: quartz scratches calcite, but calcite does not scratch quartz.
- Using only one test result is risky because mineral identification should also consider color, streak, luster, cleavage, density, and crystal shape.
Practice Questions
- 1 A mineral is scratched by quartz with hardness 7 but not scratched by orthoclase feldspar with hardness 6. What is the mineral's approximate hardness range?
- 2 Which mineral is harder: fluorite with hardness 4 or apatite with hardness 5, and which one can scratch the other?
- 3 A glass plate has a hardness of about 5.5. If an unknown mineral scratches glass but is scratched by quartz, what is its likely hardness range?
- 4 Why is the Mohs scale useful for mineral identification even though it does not measure exact hardness differences?