Minerals and Metals in Ancient India v1.c28.s8.t5.18

v1.c28.s8.t5.18

Tibetan icons contain detectable quantities of arsenic. Some weathered *fahlerz* ores of copper, containing not only arsenic but also some antimony, nickel and silver, might have been used for smelting. (Tylecote, 1962) The items 4 and 5 (Table 20.9) viz., the lion and the base of the brass Mañjuśrī however contain higher proportions of arsenic and much less of the other trace elements and therefore suggest deliberate arsenic-alloying. This 12.5 cm icon has been described by Schroeder (1981), and elemental analysis for the icon, lion and base published by Craddock (1981: 27, No. 42). La Niece *et al.* (1989) showed that like the third century BC Libyan ‘white copper’ coins, the base of the Mañjuśrī statuette (No. 5 in Table 20.9) contains high per cent of arsenic (7.4) in the bulk and even higher (14.0) per cent of the element on the surface. X-ray fluorescence and scanning electron microscopoy with EDAX analysis revealed that the arsenic-rich layer was formed due to inverse segregation which occurs in alloys freezing over a long temperature range and contracting during solidification. (La Niece *et al.*, 1989: 12) Evidently the arsenical casting alloy was chosen for the visual effect of a ‘golden’ statue on a white ‘silvery’ base. The eleventh century text *Rasahṛdaya* (18.23-69) actually described the process of “heating of copper with an equal weight of *tāla* (orpiment, As₂S₃) and *vaṅga* (tin) to convent this into silver”.