One of the easiest ways to clean marine fossils is with vinegar.
Step 1: Procedure
Add 2 cups of white vinegar into a bowl and place the marine fossil inside. The vinegar will start to foam, this is a reaction between the acetic acid in the vinegar and the limestone on the fossil. This chemical reaction dissolves the limestone on the surface of the fossil.
Let the fossil soak in the vinegar for about two minutes. After take the fossil out of the vinegar. Use a toothbrush to clean the fossil. Repeat this step as many times as you want. You may continue until the entire surface of the fossil can be seen.
When you have completed the cleaning of your fossil wash it with water and let it dry completely.
Step 2: Results
After the fossil has been cleaned, rinse it in fresh water for about one hour.
Dry your fossil in a cool dry place and never in direct sunlight.