The substance commonly used for writing on blackboards is chalk, a soft white limestone made primarily of calcium carbonate. Historically, chalk has been favored for its ability to create clear, easily erasable marks that can be used to convey information during teaching or presentations. Although chalkboards have evolved with the advent of technology, they still retain popularity in some educational settings for their simplicity and effectiveness. In recent years, chalk alternatives, such as dry-erase markers on whiteboards, have emerged, but traditional chalk remains a nostalgic and fundamental tool in classrooms, fostering a tactile and interactive learning experience.