coccolith
/ˈkɑkəˌlɪθ/
noun
- A tiny, round plate made of calcium carbonate that forms part of the outer covering of certain microscopic marine algae called coccolithophores.
- Under a microscope, the ocean water sparkled with countless coccoliths from tiny algae.
- Scientists study coccoliths in sediment cores to learn about ancient ocean climates.
- Each coccolith is so small that millions of them can fit on the head of a pin.