Crayola manufactures two types of chalk, extruded and molded. Extruded chalk, such as Crayola Anti-Dust White Chalk, primarily contains calcium carbonate. Molded chalk, such as Crayola Children's Chalk (available in white or colored), is a softer chalk, made of plaster of paris. This type of chalk is not dustless and not recommended for chalkboard use. Crayola Sidewalk Chalk is a molded chalk that is not intended for use on chalkboard surfaces. It does not include calcium carbonate. This product contains plaster of paris which has a gritty texture and may scratch your chalkboard. While Crayola Children's Chalk is generally sold at toy, grocery and drug stores, Crayola Anti-Dust Chalk is normally found at school and educational supply stores. To locate a teacher/educational supply store near you, please check your local yellow pages under “school supplies.” If you need further assistance, please call (800) 272-9652 weekdays between 9:00 AM and 4:00 PM Eastern Time and a representative will be happy to assist you.