Rocks and Minerals: Scratch Test

As always, I am excited to be back for another Saturday Science. We have missed joining in the last few Science Saturdays as we worked hard on The Ultimate Guide to Baby’s First Year.  If you are a regular here, you know how we studied rocks for some time awhile back. We have explored the rock cycleobserved rocks, explored pressure and volcanoes through fizzy science experiments and even done a Lego rock excavation. This week I am so excited to share our simple scratch test we did to explore rock hardness and the properties of rocks and minerals.

Rocks and minerals Scratch Test

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During our entire unit on Rocks, we had a basket of found and collected rocks on the kitchen table. We would leave them out as an invitation to explore, discover and ask questions. I found that having the rocks visible and accessible for the boys (6 and 8)  encouraged them to continue to think about new ways to investigate.

Rock and Minerals study

As many of you know, I follow a project approach method, using child driven questioning and inquiry to drive our learning. While our rock study never turned into a full blown project, it was still driven by the boys’ interest and intrigue. This particular experiment was created after the boys started to notice that some rocks left a residue (dust/sand) behind, yet some did not.

They wanted to know why some rocks were dirtier than others and after learning that rocks can change shape, they were curious to learn about rock hardness.

Rocks and Minerals Book for kidsRocks and Minerals Book Rocks Hard, Soft, Smooth and Rough

After reading some of our favorite books about rocks, we learned that you can test a rock’s hardness by using 2 methods (the scratch test method and the vinegar method). Using both of these methods helps to identify the rocks you have in your collection. Mark test for Rock Hardness

Rock Investigation #1 | Marking on Paper

For the first investigation, we identified two categories we were looking for: rocks that leave a colored mark on paper and rocks that do not.

What you need:

Collection of Rocks
Black and White Construction Paper
Magnifying Glass (optional but very useful)


The boys made labels for their categories, then “drew” on paper with various rocks. Having black and white allows you to see the lighter and darker dust from the rocks. The boys discovered that none of the river rocks transferred to the paper, but the some of the rocks made really neat marks on the paper.

But they wanted more. They wanted to see why this happened.

Scratch Test for Rocks

Rock Investigation #2 | Scratch Test on Rocks

Once again, the boys made labels for each category. (I allow them to use inventive spelling and approximations since this is not the focus of this lesson. However, later in the day/week we worked on learning the “tch” digraph.)

{some adult supervision is needed for this test}

What you need:

Collection of Rocks
Nails (of various sizes)
Magnifying Glass (optional but very useful)


For this experiment, use a nail to attempt to make a mark on the rock. You will notice one of two things: a) the rock will scratch, leaving a line, a crack or dust OR b)the nail will rub off on the rock leaving a silver mark on the rock

If you see a scratch, a line, or dust, this means that your NAIL is HARDER than your ROCK.

If you see a silver line on your rock, this means that your ROCK is HARDER than your NAIL.

Rock scratch test with a Nail

This is a baseline investigation. You could take this further by learning about the MOHS Scale of Hardness, conducting the acid test, and by identifying the rocks you have in your collection.

What is your favorite thing to do with rocks? Do your children have a question they want answered?

For More Learning Resources on Rocks and Minerals

Follow Dayna :: Lemon Lime Adventures’s board Everything Rocks and Minerals on Pinterest.

Rocks the Charlotte Mason Way | Jimmie’s Collage

Neighborhood Rocks | Salt the Sandbox

10 Fun Learning Activities Using Rocks | Carrots are Orange


Are You Ready for More Science Fun?

Saturday Science Blog Hop

Time for Saturday Science Blog Hop!

Visit these great bloggers for more fun Saturday Science experiments too!

Colorful Magic Milk | P is for Preschooler

Centrifugal Force | Suzy Homeschooler

Space Ice Melt Science Sensory Play | Little Bins For Little Hands

 Follow Science Experiments for Kids on Pinterest.

What is your favorite science activity? I would love to hear! connect with me on FacebookTwitterGoogle+PinterestInstagram or subscribe by email. I can’t wait to hear your ideas.


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11 thoughts on “Rocks and Minerals: Scratch Test”

  1. I love your method of leaving the materials out so that the boys can explore it at their own speed. I used to think I was pretty cool when I could use some of the rocks as “chalk” – they would write on the ground! wow! – but I had no idea I was testing the hardness of them! 🙂

  2. Love this post! I studied geology so I am a bit of a rock freak – scratching the glass with rocks is also fun as only rocks with quartz like hardness and above will leave a mark. Looking at rocks under the microscope is pretty cool too as they can reveal a whole new world! If you can get your hands on a handful of beach sand and get it under a strong magnifying glass (or microscope) you won’t be sorry ;).

  3. There is so much I love in this post! I think that introducing hardness as a relative term where they can just compare the rocks and nails is so age appropriate and still lays the foundation for later quantitative discussions. And you used so much self control in letting them sound out “scratch!” Thank you for sharing!!

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  10. Nathan

    it is a very interesting that there are so many ways to test hardness it was fun reading this post I didn’t realize it would actually work!😆

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