I might think of silk or velvet as my favorite material. I don't think I really understand υλικό; there must be a better translation.
Of course, "ore" would be the best as it is most specific but the skill is on "material" in general so we went with that word.
We often use "material" for "fabric" or "cloth" but its main usage is: "The matter from which a thing is or can be made." as shown in these dictionaries
We are of course always open to any suggestions for better translations.