Minerals and Metals in Ancient India v1.c18.s2.4

v1.c18.s2.4

The small size of furnace and high yield of metal indicate that the ore used to be roasted to oxide stage and the smelting technology was efficient. Many groups of ore-crushing pits were found near the foot of the hills. Larger pits among them measure 60 cm in diameter and 70 cm in depth. Smaller ones measure 30 cm in diameter and 40 cm in depth. The finely crushed ore was concentrated by gravity separation at the smelting sites which were invariably located near the banks of the hill streams. Ore separation devices found are smooth gently inclined rock surfaces, nearly marked with rows of round shallow pits, 3 to 4 cm in diameter and 3 to 4 cm depth. Presumably, the finely crushed ore was allowed to slowly flow down the inclined plane and by repeating this process, much of the gangue was effectively separated from the ore. Flowing film segregation, settling of the heavier ore particles in the pits and elutriation of the lighter gangue particles were the principles involved.