Rocks and minerals are not my favorite topics to teach in middle school. However, it seems like every year, students are enthralled with this subject area! Maybe it is the way certain rocks shine or the texture of some minerals. They constantly want to touch, look and compare my rock and mineral samples.

Doing labs for this unit is a must. Almost everyday, I have students comparing and identifying different minerals and rocks. However, students were having difficulty knowing whether their sample was a rock or a mineral.

As a class, we discussed the requirements of a mineral:

  1. Naturally formed solid from inorganic material
  2. The chemical composition does not vary
  3. 3D structure

And we discussed how rocks are different:

  1. Made up of one or more minerals
  2. Naturally formed solid from inorganic OR organic material
  3. The chemical composition CAN vary
  4. Structure can vary – not necessarily 3D

Yet, these rules were still a little vague and unclear to the students. So I found a way to practice applying the rules with… candy of course!

I did find the original idea online, but I now cannot find the source or website.

The basic idea of the lab is to give students several different samples of candy. Students must analyze each type by looking at the outside, and possibly even taking a small bite to see the inside! Then they decide whether the candy sample is more rock-like or mineral-like. They must provide a clear reason why they chose what they did from one of the requirements of rocks and minerals we had previously discussed.

I’ve listed some of the candies that I have used in the past and what most students have said they were. The great thing about this is that sometimes students have very good arguments for one side or another. A few times, I have thought one sample would for sure be a rock, but students gave an equally valid reason for it qualifying as a mineral! I try then to make the candy samples very clear cut as to not cause more confusion!

Candy Sample Ideas:

  • Bite-sized Snickers (Rock because it has several “minerals” or ingredients inside)
  • Marshmallows (Mineral because it has a set chemical composition.)
  • Hershey Kiss (Mineral because it has a “3D Kiss” shape and a set chemical composition)
  • Crispy M&M – I like to use crispy or pretzel rather than peanut because of possible allergies. Some classrooms are not allowed to have any nuts whatsoever! (Rock because it is made up of different “minerals” and can vary in composition)
  • Kit Kat Bar (or piece) – This is one that could go either way, but I like the reasons behind it. Some students say a rock because it has several “minerals” inside. Others say mineral, since it has a set chemical composition and layering (and since we talk about mineral fracture, it makes sense!)
  • Jelly Bean (Mineral because it has a set chemical composition)

You can really use any types of candy or snacks you might have around. Kids love it!

We ended the lab with students looking at actual samples and they had to determine whether each sample was a rock or a mineral. I picked rocks and minerals that followed the rules so as not to trick or confuse the students, and they aced it!

I think it is safe to say that this activity “rocked”!

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