Are eastern orthodox icons made of oil or charcoal?

No. The components of most portable Orthodox icons are wood (as a base) covered with linen and then covered with gesso. The paints themselves are usually derived from minerals naturally found in rocks and sands mixed with a medium such as an egg yolk/ vinegar mixture. Some artists are known to have used a "wax encaustic" method, meaning that the pigments were mixed with wax then applied to a properly treated wood panel. It is believed that Saint Luke the Evangelist used this method for his icons of the Virgin Mary, Although a more well known icon using this method is the Savior of Mt. Sinai.