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.
Coal formation. Coal is a black or brownish black combustible mineral formed about 300 million years ago when the earth was covered by swampy forests of scale tress (lycopods) giant ferns, horsetails, and club mosses. Layer upon layer of these plants died and were compressed and then covered with soil.