Chalk

Chalk is a soft, white, porous sedimentary rock primarily made of calcium carbonate. It forms from the accumulation of microscopic marine organisms, like coccolithophores, that lived millions of years ago. Chalk is commonly used in classrooms for writing on blackboards, and in various industrial applications, including construction and agriculture. Its unique properties make it effective for drawing, as it can produce a smooth, opaque line. Despite being primarily known as a writing tool, chalk also has roles in producing lime for cement and as a filler in products like paints and rubber.