The Devonian-aged Hunsrück Slate Lagerstätte is one of the most famous soft-bodied fossil deposits. Hunsrück fossils have been pyritized (replaced with pyrite/“fool’s gold” - FeS2). They occur in a black slate matrix - the result is beautiful brassy gold colored fossils on a black background. A diverse biota has been described, including trilobites with preserved legs & gills, crinoids, starfish & brittle stars, “worms”, molluscs, corals, conulariids, sponges, cnidarians, land plants, “algae”, fish, plus various unusual arthropods & echinoderms.
The Hunsrück Slate Lagerstätte occurs in the Kaub Formation (Hunsrück Slate Group, lower Emsian Stage, upper Lower Devonian) in the Budenbach area of western Germany.
Preparation of Hunsrück fossils is notoriously difficult, and many of the pyritized fossils crumble to dust from pyrite disease over many years. Recently, a “secret” air abrasion method has been successfully used to prepare Hunsrück fossils, using an abrasive grit composed of metallic iron powder mixed with potato starch.
Shown below is a pyritized, complete fossil brittle star (ophiuroid) from the Hunsrück. All five arms are bent in the same direction, indicating current direction before final burial. This is a Furcaster paleozoicus brittle star, a species first described by Bernhard Stürtz in 1886.
Classification: Animalia, Echinodermata, Asterozoa, Ophiuroidea, Oegophiurida, Zeugophiurina, Furcasteridae
Furcaster paleozoicus Stürtz, 1886 (8.5 cm long) with current aligned arms from the Hunsrück Lagerstätte (Lower Devonian) of western Germany.
Furcaster paleozoicus Stürtz, 1886 (field of view ~4.0 cm across) from the Hunsrück Lagerstätte (Lower Devonian) of western Germany.