Why is chalk a chemical sedimentary rock?

Chalk is classified as a chemical sedimentary rock because it forms primarily from the accumulation of microscopic marine organisms, particularly coccolithophores, whose calcium carbonate shells accumulate on the ocean floor. Over time, these sediments compact and lithify, resulting in a soft, white rock composed mostly of calcite. This process of formation distinguishes chalk from other sedimentary rocks that may derive from physical weathering or the accumulation of larger particles.