The metal was composed of six different metals that of Copper (Tambë), Silver (Ilsa), Tin (Latúken), Lead (Kanu), Iron (Anga), and Gold (Laurë). The six metals it was made up of meant that it had all their powers and properties as well and was extremely strong, hard, bright, and smooth. The light that shown on it and what it was exposed to caused it to vary in color. Only Aulë knew its secret.
The metal was best known for being what Melko's (Melkor) bonds were made of which were known as Angaino, the great chain, Vorotemnar, the manacles, and Ilterindi, the fetters. After Tulkas finally subdued Melkor, Aulë set his Tilkal creations on him which caused them to glow red when they touched him.