Low Rank Coal
* Lignite: Often called "brown coal", it's the youngest and least mature coal with the lowest carbon content. It has a high moisture content and burns with a lot of smoke.
* Sub-bituminous: A step up from lignite, it has a higher carbon content and burns more efficiently. It's commonly used for power generation.
High Rank Coal
* Bituminous: This is the most common type of coal, known for its high heat content and its use in power plants and steel manufacturing. It's also the main source of coal tar and coke.
* Anthracite: The highest rank coal, it has the highest carbon content and burns with a clean, smokeless flame. It's used primarily for heating and in some industrial processes.
Other Notable Types
* Cannel Coal: This rare type of coal has a high volatile matter content, burns brightly, and is often used as a fuel for lamps.
* Boghead Coal: This type is rich in algae and produces a high yield of oil and gas when heated.
Where to Find Examples
* Coal Mines: This is the most obvious source, and you can often find samples of different coal types at museums or educational centers associated with mines.
* Online Retailers: Many online retailers sell coal samples for educational purposes.
* Geological Exhibits: Museums with geological collections may have examples of different coal types on display.
Keep in mind that the appearance and properties of coal can vary significantly depending on the specific geological conditions under which it formed.