======Testing Rock Hardness======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Scratch Test: Rock Hardness
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====Summary====                   
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====Procedure====  
  -Begin by reviewing how rocks can be classified by observable features.
  -Show two rocks and ask students how they might test which is harder.
  -Demonstrate a scratch test by rubbing one rock against another; explain that a true scratch leaves a dent, while dust can be wiped away.
  -Allow students to predict which rocks will be hardest and softest.
  -Have students test at least two sets of rocks outdoors, recording results on a worksheet.
  -Guide students in ordering rocks from softest to hardest based on their tests.
  -Discuss how different rock hardness makes rocks suitable for uses such as carving, grinding, building, or tool-making.


====Links==== 
Fun Science Fridays episode 10: rock scratch test - Headwaters Science: 
{{youtube>x31RV8gSqtQ?}}\\

Identifying Minerals - Hardness Test - GeoscienceAustralia: 
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📄 Scratch test - Primary Connections: [[https://primaryconnections.org.au/teaching-sequences/year-3/dig-deep/lesson-5-scratch-test]]\\

====Variations====
  *Test classroom or local rocks (such as chalk, sandstone, quartzite) to compare hardness.
  *Use coins, nails, or glass to compare rock hardness against everyday materials.
  *Create a classroom hardness scale from 1 (softest) to 5 (hardest) based on tested rocks.
  *Use Mohr's scale and a test kit to test.



====Safety Precautions====
  *Conduct scratch tests outdoors to reduce exposure to dust.
  *Do not allow students to inhale rock dust.
  *Supervise use of hard or sharp rocks to avoid accidental cuts.
  *Wash hands after handling rocks.




====Questions to Consider====
  *What does it mean when one rock can scratch another? (It is harder.)
  *Why does dust not always mean a scratch? (Dust may come from the softer rock, not a true mark.)
  *How does mineral hardness affect rock hardness? (Rocks made of harder minerals resist scratching.)
  *Why might harder rocks be chosen for tools, while softer rocks are used for carving or building? (Harder rocks can cut or grind, softer rocks are easier to shape.)