A colorimetric method based on the blue color developed by chlorocobaltic acid in a concentrated hydrochloric acid solution has been worked out for the determination of cobalt in domestic asbolan ores. The chief impurities besides silica in such ores are large amounts of oxides of manganese, aluminium and iron together with appreciable amounts of oxides of copper, zinc and nickel. It has been found that these impurities have negligible effect on the accuracy of cobalt determination provided that suitable amount of stannous chloride is present. Consequently, it is unnecessary to remove these impurities, and the time required for each determination is only 2 hours for ore samples and 10 minutes for cobalt-containing solutions. The present method has been compared with the electrolytic method and the nitroso-R-salt colorimetric method on three samples: (ⅰ) an asbolan ore from Chianghsi, China, (ⅱ) a leaching solution of the same ore and (ⅲ) a slag obtained by smelting the same ore. The results agree very well. A detailed procedure for the determination of cobalt in domestic asbolan ores has been suggested.