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.
TYPES OF COAL Coal is classified into four main types, or ranks (lignite, subbituminous, bituminous,anthracite), depending on the amounts and types of carbon it contains and on the amountof heat energy it can produce.ignite is the lowest rank of coal with the lowest energy content. Lignite coal depositstend to be relatively young coal deposits that were not subjected to extreme heat orpressure. Lignite is crumbly and has high moisture content.