India was the world-leader in Metallurgy for more than 5,000 years. Gold jewelery is available from 3,000 BCE. Brass and bronze pieces are dated back to 1,300 BCE. Extraction of zinc from ore by distillation was used in India as early as 400 BCE while European William Campion patented the process some 2,000 years later. Copper statues can be dated back to 500 CE. There is an iron pillar in Delhi dating back to 400 CE that shows no sign of rust or decay.
The earliest know book on metallurgy was known to be written by Nagarjuna in 10th century. The book Rasaratnanakara addresses various metallurgical topics such as:
Preparation of liquids (rasas) such as Mercury
Extraction of metals like Gold, Silver, Tin, and Copper from their ores and their purification
The processes of liquefaction, distillation, sublimation, and roasting
India was invaded by Mohammedans during the time of Nagarjuna. It is possible that Nagarjuna’s texts fell into the hands of the invaders, who could have transmitted these Indian Metallurgical sciences to the outside world.