RuneScape Classic Wiki
RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Ruby Amulet
The Old School RuneScape Wiki also has an article on Ruby Amulet.

A Ruby Amulet is a piece of jewellery that can be made by using a ruby on a furnace with a gold bar and an amulet mould in your inventory. The ruby and gold bar will be consumed in the process, producing an unstrung ruby amulet. You can then use a ball of wool on the unstrung amulet to make it wearable.

Ruby amulets can be enchanted using the Enchant lvl-3 amulet spell to create a Ruby amulet of strength.

See also