Adamantine

Adamantine was a jet-black alloy of adamantium and other metals. Usually black in colour, adamantine had a green sheen when viewed by candlelight or a purple-white sheen when viewed by magical light.

It was found only in veins of ore near earth nodes and areas of faerzress in the Underdark. Occasionally, small meteorites consisting of some adamantine would fall to Abeir-Toril as well.

Applications
Adamantine, when smelted, was ultra-hard but this was a costly procedure. Adamantine weapons were useful for damaging the weapons and armor of opponents. A set of adamantine armor or a shield was nearly impenetrable to normal weapons.

Adamantine was often used by drow elves of the Underdark, and their adamantine weapons were usually swords that were magically enhanced. Their magical strength and sharpness faded if brought into contact with direct sunlight.