Wootz is a steel alloy having a pattern of bands or sheets of micro carbides within a tempered martensite or pearlite matrix. Developed in India around 300 AD, (although some say as early as 200 BC). the word wootz may have been a mistranscription of wook, an anglicised version of ukku, the word for steel in many south Indian languages.
Wootz can be made in crucibles, e.g., crucible steel by combining a mixture of wrought iron or iron ore and charcoal with glass, which is then sealed and heated in a furnace. The result is a mixture of impurities mixed with glass as slags, and "buttons" of steel. The buttons (with a typical carbon content of 1.5%) were separated from the slag and forged into ingots. The ingots could be further forged out into blades/tools or welded to other ingots to increase the mass of the steel for larger items.
Wootz steel was widely exported throughout the region, and became particularly famous in the Middle East, where it became known as Damascus steel. The critical characteristic of wootz steel is the abundant ultrahard metallic carbides in the steel matrix precipitating out in bands, making wootz steel display a characteristic banding on its surface. Wootz swords were renowned for their sharpness and toughness.