Iron as a metal has been used right from the protohistoric period in India. Iron technology appears in a developed and stable form both in Uttarapatha and Dakshinapatha as far back as 1300 BC, if not earlier. The technology of Iron seems to be a native development.
The term 'ayas' meaning iron occurs in Vedic literature. Iron smelting workshops have been found at the site of Naikund.The remarkable aspect of the technology of these people was the combined use of iron and copper. This site is dated by the carbon-14 method to the seventh or eighth BC . We have obtained from Maharashtra and Andhra, daggers with iron blades and copper hilts, pots encased in copper sheets riveted with iron pins and many other things. The mines in Anantapur and other mines in Andhra and Karnataka might have been the source for metals like iron, copper, etc... for the Megalithians.
Most of the objects that have been found are weapons of war such as daggers, swords,etc. Among the objects of general use are nails, sickles , pans and ploughs. A few other objects of domestic and ritual use also have been excavated.
Iron technology had advanced a lot in the early historical period, from the times of Mahavira and Buddha. Recent excavations have now established that an ancient royal house that ruled which ruled Andhra Pradesh and parts of Maharashtra and Madhya Pradesh between the fourth and sixth centuries AD, minted coins of iron. These coins of iron are of a high quality, almost like steel. The coins are somewhat corroded and circular in shape. Analytical studies of these coins from Vidarbha were undertaken by chemists very clearly revealed that they are of iron with copper and tin ternary alloys. In recent archaeological excavations at the ancient cities of Andhra Pradesh, several coin types were found wholly cast in iron. The excessive rusting of the iron coins made them heavier in weight and somewhat distorted in shape and size. In some coins copper, silver and sometimes, even a gold film is noticeable which appears as a thin coat on both sides. The symbols on these issues have a political and artistic significance. It is necessary to document properly and study these interesting and unique coin symbols with insight of an art historian.
The lion and temple types among the Vishnu Kundin coins from Amaravati and the Peddavegi excavations, like the lone group of tribal coins of Audumbra chiefs,(2nd-3rd century AD) represent Mahasena or kartikeya symbolically, the 'Sriparvata Swami' or the family deity of the Vishnu Kundins. These coin types herald an independent Vishnu Kundin lineage. They were obtained from the post-Ishkvaku levels at Vijayapuri and Amaravati and were assignable to Govindavarman I justifying his title, " Purvapara Kshitipati - Parampara - hara madhya nirupama virajita Kaustubhayamana yasojanmanah", or " the peerless Kaustubha gem in the centre of the necklace that is the succession of the earlier and later kings of Sriparvata". The lion was the royal 'lanchchana' as seen from the earliest royal seals of the Vishnukundins.
It appears that between the fourth and sixth century AD, the technology of Iron had reached great heights both in North and South India. A unique example of a rust resistant pillar, 7.20 metres height is now in the old city of Delhi within the ruins of the Qutub Minar. Being a technical masterpiece, the Islamic rulers reinstated in the court of the Quwwat-ul-Islam mosque. This is an example of great artistic merit, known for its fine capital. This elevated pillar was set up as a standard 'dhvaja' of Lord Vishnu on the hill known as Vishnu Pada in the memory of the mighty ruler Chandra, identified with Chandragupta II of the imperial Gupta dynasty.