Note: Chlorhexidine may cause staining of the tooth, tooth filling, and dentures or other mouth appliances. Tetracycline use during tooth development phases (from the last half of pregnancy through eight years of age) may cause permanent discoloration (yellow, gray, brown) of teeth.
What is Coal made of? Coal is made from trees or plants that decayed on the ground for millions of years. The remains of various plants and trees then mixed with the other components of the ground and eventually going through several natural processes making them more like solid rocks.
The three main ranks of coal are lignite, bituminous coal, and anthracite. Lignite is closely related to peat but has a lower moisture content. It has the lowest heating value of any of the ranks of coal. Bituminous coal is more dense than lignite and is black in color.