This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
"When shall we three meet again?
In thunder, lightning, or in rain?"
"Macbeth" Act 1, Scene 1
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2. - The Thunderstone
Already the Roman scholar Pliny describes them as "Idaei dactyli" (the fingers from the mountain Ida). In Germany until the early 20th century people believed in the magic properties of the devil´s fingers, known also as catstones, thunderstones, wombstones or even candles of the dead. According to ancient lore these strange stones are falling from the sky and witches can use them to cause thunderstorms.
Fig.1. Conrad Gesner´s 1565 illustrations of thunderstones or Belemnites, from "De Omni Rervm Fossilivm Genere" (image in public domain).
Another myth interprets these fossils as petrified lynx urine. In fact rubbing the stone a smell of ammoniac or decomposed organic matter can be perceived, also the color of some fossils - yellow or brown, as found in the cretaceous sediments from Northern Germany - maybe explains this strange connection.
Today the belemnites are reclassified as the internal shells of extinct mollusks.
Fig.2. Belemnite from the Jurassic fossil site of Solnhofen (Germany). This fossil preserves not only the inner shell of these extinct mollusks, but also traces of soft tissue.
