Ask-a-Geologist #4: Why do geologists tests rocks for calcite?

Today we have another great geology question from one of our readers. 

Terrance writes:  Why do scientists check rocks to see if they contain calcite?

Well Terrance, calcite can be a good indicator mineral for determining the type of rock you have. Calcite is a mineral made of calcium carbonate. Common rocks that contain calcite are forms of sedimentary limestones and metamorphic marbles. Calcite will react with an acid like hydrocloric acid and some household acids like vinegar and lemon juice.

To test the rocks, you can pour the acid onto a sample and watch for the fizz or bubbles to appear on the rock. If you use a weak acid like vinegar or lemon juice you might want to use a hand lens, like this one, to see the bubbles. Geologists call this the “fizz” test. If you test your sample and see the fizz, you know that the sample contains calcite and you are on your way to identifying your rock. Click here to download the instructions for the calcite fizz test.

Remember to keep your questions coming in through the dig into geology section on our website or email us at Please comment below and subscribe to our channel to get answers to our next great question. Until next time, rock on everybody!


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