Surname: Brown coal
other names: Turff
mineral class: Elements
chemical formula: C
Chemical elements: Carbon
Similar minerals: Charcoal, hard coal
colour: dark brown, black
crystal structure: /
mass density: 1,3
magnetism: not magnetic
Mohs hardness: 2,5
stroke color: black
General information about lignite:
Brown coal describes a sedimentary rock that has a loose texture and a dark brown to almost black color. It shows a wood-like appearance and is of fibrous structure. As an important fossil energy source, lignite is used to generate electrical energy and heat. With a water content of about fifty percent, their calorific value is about thirty percent compared to hard coal.
Simple explanation of origin and occurrence:
The source material for lignite was organic, plant matter, which already colonized the earth 350 million years ago. In the swamps and jungles huge, tree-high ferns, horsetails and Bärlappgewächse grew. Dead plant material in the swamps was completely covered by water and thus exposed to a completely oxygen-free environment, whereby a decomposition was only partial. The remnants of the organic material were deposited over millions of years and were covered by sand, mud and rocks. These layers exerted such a pressure that pushed the plant material ever deeper into the earth's crust and at the same time compressed. The process of so-called carbonization began as the temperature increased, removing water and oxygen from the organic material and increasing the carbon content. That period of geological history in which this evolution took place is called Carboniferous. The name derives from the Latin word "carbo" for coal.
In the course of the coalification first peat is formed, from which then lignite and later hard coal develops. The lignite itself originated about twenty to forty million years ago and is therefore a recent result of coalification. Since it is covered by only a few layers of sedimentary rock, it is located in shallow depths of the earth's surface and is usually mined in open-cast mining. Lignite is mined all over the world, and the chemical composition may vary significantly depending on the deposits. Depending on the carbon content, a distinction is made between the soft brown, the hard brown, the matte brown and the lignite lignite. The economically most important deposits are in Germany, in the United States, Greece, Russia and Australia. These countries together support about half of the world's lignite.
Use by humans:
In addition to oil and natural gas, lignite is one of the most important fossil fuels and is used in power plants in ground and dried form for the production of electricity and heat. As the burning of lignite causes the emission of large quantities of the greenhouse gas CO2, the use of this raw material has been gradually decreasing for several years in favor of renewable energies. Like hard coal, lignite can also be used in industry to produce methanol and ammonia by producing a synthesis gas. In the course of so-called coal hydrogenation, it is also possible to use lignite as a raw material for the production of fuels.