Aule now gathered six
metals, copper, silver, tin, lead,
iron, and gold, and taking a portion of each made with his magic a
which he named therefore tilkal, and this had all the properties of the
six and many of its own. It's colour was bright green or red in varying
lights and it could not be broken, and Aule alone could forge it.
he forged a mighty chain, making of it all seven metals welded with
to a substance of uttermost hardness and brightness and smoothness, but
of tilkal he had not sufficient to add more than a little to each link."
- The Book of Lost Tales,
Chaining of Melko', J.R.R.Tolkien