Copper in Ancient India c11.s2.6

c11.s2.6

As regards the actual method of manufacture of blue vitriol in ancient India very little is known and no description of the process is to be found in alchemical works. As blue vitriol, however, is mentioned in medical works composed as early as the 3rd century B.C., it is very likely that it was obtained as a natural product or by-product in copper mines. An indigenous process of manufacturing blue vitriol along with ferrous sulphate and alum still survives in various parts of Rajputana where these sulphates are obtained by dissolving shales in water and crystallising from the solution obtained. The process was thoroughly examined and described by Colonel Brooke.² Ball in his Economic Geology of India writes—"In 1864 there were twenty of these factories at Khetri and about double the number at Singhana. The broken shale from copper mines which contains the salts is placed in earthen gharās, together with the crusts from the refuse heaps of previous lixiviations and water is added. The gharās are arranged on ledges prepared for the purpose on the heaps of refuse.