the.com/chalk
the fossilized corpses of trillions of plankton, now teaching your kids algebra
made ofcompressed skeletons of ancient marine microorganisms
cliffsDover's white cliffs are pure chalk seabed
gymnast secretchalk-dries hands to kill the slip
not in classroomsschool chalk is now usually gypsum
climbingevery chalk bag holds magnesium carbonate