Mini Me Geology Blog

Many rocks can look alike. Sometimes telling the difference between a limestone or marble and other rocks such as shale and quartzite can be difficult. One way geologists test the rocks is by performing the acid or “Fizz” test. Calcite is the main component of limestone rocks and its varieties like oolitic limestone, fossiliferous limestone, coquina and marble. The calcite mineral is made of calcium carbonate which reacts with acid. Other varieties of calcium carbonate minerals such as aragonite and dolomite will also fizz during this test.

You will need:

• Household acid such as lemon juice or vinegar (lemon juice works best).
• Minerals and rocks to test
• Eye dropper or straws
• Hand magnifier
• Notebook
• Pencil
• Camera (optional)

Step 1: Gather the samples you want to test. Some good choices are limestone, oolitic limestone, coquina and marble. You should see some “fizzing” with these samples.

Step 2: Drop, using a straw or dropper, or pour your acid on one rock sample at a time.

Step 3: Look through your hand magnifier right away to see the bubbles. The bubbles may be small so look closely.

Step 4: Observe and document your results. Do you see the bubbles? If so, what do they look like? The fizz is telling you that your rock contains calcium carbonate.

Teacher and Parent Tip: Use other samples such as shale, slate, and quartzite to observe samples which should not “fizz.” Mix up your samples and see if you can figure out what they are using the fizz test! If you have access to hydrochloric acid, it provides the best reaction with calcium carbonate but children should only use this acid under strict supervision.

You can find more great activities like these in our Rock Cycle Kit and Rock Detectives Kits! Our My Rockin’ Collection Sedimentary Rocks will teach you about several varieties of limestone that fizz!

Filed under: Geology / Earth Science, Rocks - Igneous, Sedimentary & Metamorphic on April 28th, 2014