d031b852_ध_रस_यन___क__स_च____व_क_प_ड_य___Source_and_description
[Chemical name] magnesium carbonate [Chemical formula] MgCO3 [Common or alternative name] Athlete's chalk [Source and description] 
Often sold as a powder in sporting goods stores for gymnastics, weightlifting, and climbing to help keep hands dry. Sometimes it is combined with calcium carbonate in this use. Available in tablet form as an antacid. Some antacids are pure while others are blended with calcium carbonate.
सरलता से उपलब्ध रसायनों की सूची - विकिपीडिया