Answer:
Chalk
Step-by-step explanation:
Chalk is mainly made out of calcite which is a carbon-based mineral-derived from the calcium carbonate skeleton of plankton. When plankton dies and sinks to the ocean floor, the inner delicate part of the plankton easily decays and disintegrates while the tough rigid skeleton is left behind. Accumulation of these sediments creates the sedimentary rock- chalk due to increased pressure and temperatures from overlying sediments layers.