Celadonite is a mineral that belongs to the mica group and is commonly found in shades of green or gray. Some synonyms for celadonite include glauconite, hamlinite, and heulandite. Glauconite is a greenish mineral that is commonly found in marine environments and is commonly used as a fertilizer. Hamlinite, on the other hand, is a rare mineral that is only found in a few locations around the world. It is a brownish-green mineral that belongs to the mica group and is used as a decorative stone. Heulandite is a mineral that is found in a variety of colors, including green, red, and white. It is commonly used as a decorative stone, as well as in jewelry and other applications.