Cuttlebone
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Cuttlebone is a hard brittle structure found inside cuttlefish. It is made mainly of calcium carbonate. The cuttlefish use it to control floating. Cuttlebones have been used to make polishing powder. This was then added to toothpaste. Today, cuttlebone is mainly used for caged birds and turtles, so they get their calcium.