These stains are, in reality, extractive stains that result from a chemical reaction between the extractives and iron. Most frequently, iron stains are an inky blue-black color with a distribution dependent upon the type of iron exposure. The color is more intense on some wood, especially redwood, cedar and pine, but can occur to some degree on almost any wood. A distinct rust red stain can appear on iron contaminated cedar under humid conditions do to the reaction of the extractive component of cedar called thujaplicin.