Iron 12 Iron age 10 Zinc 6 Copper 5 Manganese 5 Antiquities 4 Boron 4 Sulfur 4 Bronze age 3 Calcium 3 Iron catalysts 3 Molybdenum 3 Phosphorus 3 Potassium 3 Steel 3 A STUDY OF NORTHERN BLACK POLISHED WARE CULTURE-- AN IRON AGE CULTURE OF INDIA 2 BORON 2 Building, Iron and steel 2 COPPER AND ZINC 2 Chemical analysis 2 Chemical composition 2 Chlorine 2 Cobalt 2 Crop quality 2 Excavations (Archaeology) 2 Heavy metals 2 Historiography 2 IRON AND MANGANESE 2 India-Civilization 2 Magnesium 2