Metallurgy of iron in ancient India was studied using chemical and metallographic analysis of a large number of excavated objects from the following sites belonging to different periods of Indian history:

1. Dwarka, Gujarat (1500-1200 B.C.)
2. Tadakanhalli and Komaranhalli, Karnataka (1200-1000 BC)
3. Khapa, Tkalghat, Mahurjhari, Arni, Central India (700-400 BC)
4. Allahapur, Uttara Pradesh (400-300 BC)
5. Soron, Uttar Pradesh (600 BC-1000 AD)
6. Attranjikhera, Uttar Prdesh (600 BC-500 AD)
7. Jajmau, Uttar Pradesh (600 BC-500 AD)
8. Hulaskhera, Uttar Pradesh (400 BC-500 AD)
9. Sringverpura, Uttar Pradesh (250 BC-600 AD)
10. Kausambi, Uttar Pradesh (800 BC-500 AD)
11. Khairadih, Uttar Pradesh (100-400 AD)
12. Manjhi, Bihar (600 BC-500 AD)
13. Nadural Meghalith,Kerala 600B.C
14. Raj Nal Ka Tila, U.P1300B.C

Chemical analysis of the samples showed that all the objects contained silica, alumina, lime and manganese as impurities in the iron. The presence of silica, calcium and manganese in very low amount indicates that the metal used in these artefacts was extracted from ores and no meteoric iron was used.

Metallographic studies were carried out to obtain information on:

1. Technique of fabrication of the objects.
2. Mode and degree of carburisation of iron to make steel.
3. Heat treatment given to the objects to improve properties of the steel.

From the result of the studies on the artefacts from all the seventeen (17) sites and after reviewing the work done by earlier archaeo-metallurgist from all over India, the following conclusions can be drawn:

1. Use of iron began around 1500-1200 BC in the western region (Gujarat).
2. Lamination technology (layering technique) using wrought iron and high carbon steel sheets alternately to fabricate weapons and tools, was developed in South India in around 1200-1000 BC. The technology reached the hands of smiths of Central India by 700-400 BC and that of Uttar Pradesh by 600 BC.
3. Case carburisation technique was developed in around 600 BC in Central India (Maharashtra) and Eastern Uttar Pradesh almost simultaneously.
4. Heat treatment of medium and high carbon steel tools was developed by 600 BC-300 AD in Eastern Uttar Pradesh and Central India (Maharashtra).