How to Test a Rock for Calcium Carbonate

Testing a rock to see if it contains calcium carbonate is a basic part of any introductory level geology class. This test could become increasingly important because rocks that contain calcium carbonate can be made to release their carbon in the form of carbon dioxide, "the greenhouse gas" that contributes to global warming. This simple test can tell you if a rock contains calcium carbonate.

Things You'll Need

• Vinegar
• Plastic cups
• Specimens to test

Instructions

1. Place each specimen in a plastic cup.

2. Pour vinegar over each specimen, just so they are barely covered.

3. Let the specimens sit for several hours, or even overnight.

4. Look for bubbles on the specimens. The presence of bubbles indicates the presence of calcium carbonate. The vinegar reacts with the calcium carbonate to produce calcium acetate, water and carbon dioxide.

5. Observe the specimens every five minutes at first, then less frequently, making your final observation in the morning.

6. Try some specimens other than rocks, such as egg shells, sea shells, anti-acid tablets and chalk. These will all produce very nice bubbles.

Tips & Warnings

• Limestone is the most common rock that contains calcium carbonate.