Charcoal

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Luster (hard) coal from the Ruhr carbon
(shown in the German Mining Museum )

Bright coals are different types of coals that have a strikingly shiny surface. The luster goes back to the increasing conversion of plant residues into the maceral vitrinite, which takes place when the remains are covered with younger sediments . In the case of hard coal , one speaks of vitrite , whereas in the case of lignite it is called lignite .

The gloss allows only limited conclusions to be drawn about the other properties of the coal. The gloss is usually associated with a deep dark / black color and greater hardness and brittleness . The gloss is usually an indication of advanced coalification . Most hard coals and especially anthracite coals have a pronounced metallic or glassy sheen (see picture).

Luster brown coal

Even with lignite , a gloss develops with increasing coalification. The natural Inkohlungsreihe following, the gloss brown coal a transitional stage from lignite to bituminous coal. In particular, such a glossy brown coal is often just as lustrous carbon designated as unusual on lignite of shine and also gives an indication of higher quality, while common in coal so is that it is not a distinguishing feature that requires special mention in the name. In the southern Bavarian lignite districts, the lignite lignite was called pitch coal .

Under special geological conditions, even relatively young lignite, which normally has a rather dull / dull surface, can exceptionally develop a gloss: For example, it can occur in lignite deposits in volcanically / geothermally active areas (e.g. on the Meißner ), that the lignite is exposed to elevated temperatures that lead to natural pyrolysis (coking) of the coal. This coking leads to an increase in the calorific value , but as a visible sign it also makes the surface darker and (just as with artificially produced coke and charcoal made from wood rich in resin) noticeably shiny.

Individual evidence

  1. ↑ a b c H. Murawski, W. Meyer: Geological dictionary. 11th edition. Spectrum Academic Publishing House, 2004, ISBN 3-8274-1445-8 .
  2. ^ Zoltán Faragó: Fuel Science. Lecture notes. on: www.farago.info (PDF; 1.1 MB)
  3. ^ Mining on the Meißner - 400 years of coal for salt. ( Memento from February 3, 2014 in the Internet Archive ) Excerpts from the speech by Berghauptmann a. D. Dr. Schade, Wiesbaden, on the occasion of the inauguration of the miner's relief at Schwalbenthal on the Meißner on October 28, 2003. online at: wallbraun.wa.ohost.de