what type of rock is chalk

Chalk is a soft, white, porous, sedimentary carbonate rock. It is a type of limestone composed primarily of the mineral calcite (calcium carbonate) and originally formed deep under the sea from the compressed remains of microscopic marine plankton such as coccolithophores and foraminifera. Chalk typically contains 90-99% calcite and may include minor amounts of other minerals like quartz, clay, and flint nodules. It is distinguished by its fine texture, light color, softness, and high porosity.