Coral Tube Sample
Coral Chunk is a Material gained by harvesting a Coral with the Knife.
One of the easiest ways to gather coral chunks is by using the Knife (RMB) on the beige, tube-shaped pieces of coral, often found near the surface of the water. These can be found in the Safe Shallows biome.
Coral Chunks can be refined to Calcium using the Fabricator.