Willemite, Franklinite, are two different minerals, which always appear associated in the deposit of this locality (Franklin, New Jersey, in the USA). Franklinite is an oxide of zinc, iron and manganese. On the other hand, Willemite is a zinc oxide with silicon. This mineral is highly fluorescent, giving a very striking green color. This association of minerals is also accompanied by Calcite, which provides an intense pink tone in ultraviolet light.
