Bleiberger shell marble

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The Bleiberger shell marble , also called helmintholite and opalescent shell marble, is a rare rock that was first found near Bad Bleiberg in Carinthia , Austria , in 1780. This rock, known as marble , is classified as a shell limestone because it was not changed by any rock metamorphosis. The sedimentary rock , which the botanist and mineralogist Franz Xaver von Wulfen referred to as the “Carinthian peacock-tailed helmintholite”, originated in the lower Upper Triassic .

Rock description

The Bleiberger shell marble is composed of fossilized limestone shell remains of ammonites , especially Carnites floridus . The shell marble was, because of its play of colors in gold-green and gold-red colors, after its discovery, a very popular jewelry material. The play of colors is related to the remains of the shell in this brownish-red shell limestone, which shimmer like a mother of pearl depending on the incidence of light. The colorful play of colors is based on interference phenomena of the parallel oriented crystals of aragonite minerals in the mother-of-pearl layer of the bowls.

Discovery and Use

This rock was first described by Franz Xaver Wulfen, who drove the geological and mineralogical exploration of Carinthia. Wulfen and the early geologists assumed that the shell marble would become opalescent through "temper colors as a heel of subterranean water or as a hint of subterranean air". On numerous excursions, Wulfen collected pieces of rock, fossils and minerals for what was then the "Mineralienkabinett" in Klagenfurt and described for the first time the "opalescent shell marble" and the fossils that appear in it, such as ammonites ( Nautilus flondus , Nautilus bisulcatus , Nautilus nodulosiv and Nautilus nodulosiv and Nautilusiv ) the clam Cardium triquetrum .

From this rock, which was discovered in the St. Oswaldi tunnel near Bleiberg during lead ore mining in 1780, numerous jewelry items were made at the time. In 1991 two of these rare silver mounts were offered at auction. One of these cans was auctioned by the Natural History Museum Vienna and another, which was later offered, by the State Museum of Carinthia . Only a few jewelry items have survived to this day. Bleiberger shell marble was used for rings, brooches, pendants, boxes or for table inlays. The stone seemed so important that the tunnel entrance was lined up with a door by order of the Austrian court and locked to prevent unauthorized removal. A stone table was also to be made from this shell marble for the Tsarist court in Russia.

A find of the Bleiberger shell marble is also in the rock collection of Johann Wolfgang von Goethe . The small deposit was depleted about three years after its discovery.

Further occurrences of shell marbles

Another occurrence of the rare shell marble is said to be on the Lavetscher Joch near Hall in Tyrol in Austria. It is assumed, however, that this deposit did not exist, but that collectors appropriated pieces of the Bleiberger shell marble before and after the order of the Austrian court. This new deposit was reported shortly after the tunnel in Bleiberg was closed and the mineral similarity of the pieces of stone supports the assumption that the deposit in Tyrol was simulated.

Shell marbles with the play of colors of ammonites are found at Jelatma on the Oka in European Russia , at Folkestone in southern England, at Bakulites in Wyoming and at Lethbridge in Alberta , Canada .

Web links

Individual evidence

  1. ↑ Johan Jakob Palm: Xaver Wulfen's treatise on Carinthia's peacock-tailed helmintholite or the so-called opalescent shell marble . Erlangen 1793. Online on Google Books , accessed June 17, 2010.
  2. ↑ a b Natural History Museum Vienna , accessed on June 16, 2010
  3. ↑ a b c Gerhard Niedermayr: The Bleiberger shell marble - FX Wulfens 'Carinthian peacock-tailed helmintholite'. A historical consideration. Online at biologiezentrum.at (PDF file; 11.46 MB). Retrieved June 17, 2010
  4. ↑ Karl Krainer (lecture manuscript): Some data on the geological exploration history of Carinthia online at geologie.ac.at (PDF file; 520 kB). Retrieved June 16, 2010
  5. ↑ a b Gerhard Niedermayr: A box made of Bleiberger shell marble for the State Museum in Carinthia on biologiezentrum.de (PDF file; 3.85 MB) Retrieved on June 16, 2010
  6. ^ Hans Prescher : Minerals and rocks from Austria in Johann Wolfgang von Goethe's collections in Weimar . Retrieved on June 16, 2010 online at haben.at