Siegburgite (Cottbus Fm., 25.5-23.5 Ma [min.])

"Siegburgite"

Goitzsche Opencast Mine

Bitterfeld-Wolfen, Saxony-Anhalt State, Germany

Bernsteinschluff Horizon

Cottbus Fm. (25.5-23.5 Ma [min.])

Chemical Composition:

C: 81.37%, H: 5.26%, O: 13.37%, Cinnamic Acid: 0.0073%

Specimen A (Top Left): 0.4g / 14x12x6mm

Specimen B (Top Right): 0.5g / 14x14x8mm

Specimen C (Bottom Left): 0.3g / 14x12x4mm

Specimen D (Bottom Right): 0.2g / 13x10x4mm

*I did not take a photograph of these specimens under longwave UV, due to the fluorescent response of Siegburgite being so weak; they fluoresce a dull burgundy.

Siegburgite is referred to as an "accessory resin", but is considered a true amber. It occurs alongside several other accessory resin species, as well as the more well-known Bitterfeld amber. Siegburgite is a fascinating amber, and is one of the few fossil resins classified as a Class III resin; it is essentially a natural polystyrene, found as concretions where it is a binding agent to fine sand and mica: the sand is often evenly distributed, and is variable in proportion to the resin, occasionally more than 60%. Siegburgite is highly flammable.

Siegburgite was produced by a plant of the genus Liquidambar (Hamamelidaceae Family, also commonly known as the "witch-hazel" family): within the fresh resin, known as storax or copalm balsam, cinnamic acid and esters quickly decarboxylate (chemical reaction that removes a carboxyl group, and releases carbon dioxide), forming styrene; upon its burial, the newly-formed styrene underwent polymerization over tens of millions of years, as it became polystyrene.

It is found in the lignite (German: "Braunkohle"), lignite-sand, and lignite-clay layers of the upper portion of the Cottbus Formation; Bitterfeld amber is also found within this Formation. The amber- and accessory resin-bearing layers are situated beneath the Bitterfeld Main Coal Seam, and above the Breitenfeld Seam. The Goitzsche Mine, from which Siegburgite and other fossil resins were obtained, opened in 1949 and closed in 1991.

Sources:

"Siegburgite, a new Fossil Resin."; Jahrbuch für Mineralogie 1875; pp. 128-133; A. V. Lasaulx

"Roman Amber Identified as Siegburgite"; p. 12; Dietz, Catanzariti, Quintero, Jimeno 2013

"The System of Mineralogy of James Dwight Dana 1837-1868: Descriptive Mineralogy"; p. 1005; Dana 1892

"Biology of Amber-Producing Trees: Focus on Case Studies of Hymenaea and Agathis"; p. 9; Jean H. Langenheim 1995

"The First Fossil Cyphophthalmid (Arachnida: Opiliones), from Bitterfeld Amber, Germany"; Jason A., Gonzalo Giribet 2003

"Geography - Coal Mining in the Goitzsche/ The geology of the Goitzsche"; Europagymnasium Walther-Rathenau-Bitterfeld Comeniusprojekt

"Die Bernsteinlagerstätte Bitterfeld, nur ein Höhepunkt des Vorkommens von Bernstein (Succinit) im Tertiär Mitteldeutschlands"; Fuhrman 2005

http://www.regionalgeologie-ost.de/Abb. 23.11 Halle-Merseburger Tertiaer.pdf?fbclid=IwAR1RiYz3wsaHe-k20RnzaZv4jZt29VpR9oxrndNKKQ7ueDaygvpPC4peqVQ