History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c30.s1.9

c30.s1.9

There are two varieties of copper: the one brought from Nepal is of superior quality; that dug out of mines of other countries is designated *mlechchha* 44
(Mlechchha is a generic name for a barbarian or a foreigner )
Copper-leaf is killed by being rubbed with lemon-juice, sulphur and mercury and roasted thrice (sulphide of copper). 55