This is a polished Amphibolite artifact with bilaterally, somewhat irregularly grooves on both sides found in the 1960ies at a LBK-site near Göttingen (Lower Saxony; Germany). The finder, suggested its use as an Arrow shaft polisher, but it has to be remembered, that arrow shaft polishers in the Central European Neolithic consist mostly of sandstone and usually have a have a flat and a curved area. On the flat side a U-shaped groove was made. It is believed that these stones were placed in pairs with the flat side against each other to grind on arrow shafts or other organic material, which was to be polished. In my view, the artifact displayed here is a semi-finished pair of two flat adzes or shoe-last adzes and the grooves were made to separate the rough outs of the two adzes from each other.
Amphibolite is a fine grained and hard matamorphic rock which played an eminent role in the raw material supply of Middle European Early and Middle Neolithic communities.
In 1996 isotopic data were published, that indicate that most of the amphibolite raw material used for flat-axes and adzes during the Early and Middle Neolithic throughout Germany point roughly to a Proterozoic age of the stone used; an age which can be reasonable matched to a single outcrop situated at Jistebsko within the Czech Republic.
Long distance transport (800-1000 km) of raw materials were not uncommon during the Neolithic of Europe. For example, a small group of shaft-hole axes found in northeastern Italy were made from amphibole originating from the southern thermal aureole of Tanvald granite in northern Bohemia.