* Limestone: It's a sedimentary rock primarily composed of calcium carbonate. It forms from the accumulation of shells, skeletons, and other marine organisms.
* Chalk: It's a soft, white, porous form of limestone. It's made up of the microscopic shells of marine plankton called coccolithophores.
While they're both calcium carbonate, they differ in their origin, texture, and appearance:
* Limestone is typically denser and harder than chalk.
* Chalk is very porous and crumbles easily.
Both limestone and chalk are important materials with many uses:
* Limestone: Construction material, cement production, agriculture (soil amendment), and more.
* Chalk: Writing material, blackboard chalk, and a component in some medicines.
