The protoscience that we know as alchemy—the admixture of various substances with the purpose of producing a new substance with different properties—made its way to Europe by way of the Arab world. The Arabs acquired their knowledge of alchemy in their conquest of Persia. And the Persian learned it from their neighbors to the south in India. It was never a secret to the nations of the classical world that the very best metals came from India. When Alexander the Great conquered the Indus River valley, the vanquished King Porus chose to present to him as tribute not gold or silver, but 30 pounds of Indian steel.
It is said that by 300 BC, the Indian civilizations had already perfected the craft of forging steel. They produced an alloy that was very high in carbon called wootz steel. It was very light, very durable and, according to legend, could be honed sharp enough to split a hair the fell across its blade. Throughout the middle ages India shipped ingots of wootz steel to the Middle East where it was forged into formidable weaponry which the European crusaders ruefully termed Damascus steel.
Swords forged from Damascus steel have a distinctive branding pattern resulting from the dissolution of carbides into the ore while under intense heat. A great many Damascus blades still exist today as artifacts, but a new blade has not been forged in over 300 years. The technology for alloying wootz steel and fashioning Damascus blades has been forgotten. It is today a lost secret of the pre-modern world. Metallurgists have attempted to reproduce the technique by analyzing the chemical make-up of surviving samples of Damascus steel and working backwards from there. They have yet to craft an accurate replica. Yet another riddle whose answer the Indian alchemists keep with them in the past.