The Hunsrück Slate () is a Lower Devonian lithostratigraphic unit, a type of rock strata, in the German regions of the Hunsrück and Taunus. It is a lagerstätte famous for exceptional preservation of a highly diverse fossil fauna assemblage. Geology The Emsian stratigraphy of the southern Rhenish Massif can be divided into two lithological units: the older slates of the Hunsrück-Schiefer and the younger sandstones of the Singhofener Schichten. Stratigraphically below the Hunsrück Slates is the (older) Taunus quartzite. All these metasedimentary rocks were originally deposited in the marine Rhenohercynian Basin, a back-arc basin south of the paleocontinent of Laurussia. The Hunsrück Slate roughly comprises the Sauerthal-Schichten, Bornich-Schichten and Kaub-Schichten. These are 408–400 Mya old, making them part of the Latest Pragian to Early Emsian stages of the Devonian. History of mining The Hunsrück slate was a source for Rhenish slate over several centuries. Archaeological finds in West Germany show that the slate was used in Roman times. The first documented case of mining in this area dates from the 14th century. The production continued with the Industrial Revolution at the end of the 1700s, but in 1846–49, the industry fell into crisis, resulting in poverty and misery in the mining areas. The economic upturn after the Franco-Prussian War of 1870-71 resulted in a renewed increase in slate production, where companies used more extensive pits. Production continued until the 1960s, when the competition from cheaper synthetic or imported slate resulted in production decline. Only a single pit in the Bundenbach region was worked in the 1990s. Since 1999, slate imports from Spain, Portugal, Argentina and China caused the abandonment of local mining. Mining of Hunsrück slate was important for the discovery of fossils. Although not rare, fossils can only be found through extensive mining of slate. Many of the fine fossils exhibited in museums today were originally found by the slate miners. The first scientific publication on these fossils comes from Ferdinand von Roemer (1862), who described starfish and crinoid fossils from Bundenbach. German paleontologists such as R. Opitz, F. Broili, R. Judge, and W. M. Lehmann studied many fossils between 1920 and 1959. Lehmann's death in 1959 and the decline of the slate industry caused a decline in fossil research. In 1970, Wilhelm Stürmer, a chemical physicist and radiologist at Siemens, developed a new method to examine the Hunsrück slate fossils using medium energy X-rays of 25-40 keV. He