As cement, authigenic mineral or vein, dawsonite is found not only in marine dolomite and oil shale, but also in terrigenous fragmentary rock and coal measures. Abundant instances and experimentations on synthetic dawsonite indicate that carbonic acid or excess carbon dioxide is necessary for generating dawsonite. Therefore, occurrence of dawsonite is always associated with carbon dioxide gas reservoir. Two genetic types of dawsonite, namely inorganic and organic are divided in response to origin of carbon dioxide. Inorganic genesis includes magmatic origin and carbonate decomposition origin. However, dawsonite can be acted as trace mineral suggesting migration or accumulation of fluids with abundant carbon dioxide to whatever origin it belongs. In geological background, occurrence or enrichment of dawsonite indicates that migration or accumulation of carbon dioxide with large scale has happened.