sticks of chalk aligned on table

aerial albus aligned another breaks brittle caco3 calcium carbon carbonate chalk chalkboards color compacted compressed concave cut cylinders cylindrical drag drawing dyes earth education geology historically horizontal lack linear marking mass mined molded multiple natural nestle next one organic oxygen particles pattern pressed produced resource rock rod rods round row schoolhouse science sedimentary sediments shaved shells slateboard sticks table tests tidy tool view white whole write writing