Determination of the origin of unusual glass with metallic spherule inclusions found in the area between Inzingkofen and Sigmaringen (Bavaria, Germany), South-West of the Steinheim-Ries Craters

This paper reports the characteristics of a suite of pale green glass fragments and their metallic spherule inclusions (5 to 400 ?m) found over a relatively wide area between Inzigkofen and Sigmaringen (Bavaria, Germany), about 150 km SW of the Steinheim-Ries impact craters. The distribution area of these glasses and their close macroscopic similarity (apart from the spherules) with moldavite suggested us that they may shed new light on the nature of the binary asteroid which caused the Steinheim-Ries impact craters. However, our petrographic and chemical data rule out an extra-terrestrial origin. Metallographic microstructure, lack of Ni and high P contents (up to 9 wt.%) reveal the metallic inclusions as cast iron spherules. The chemical composition of the host glass consistently differs from both moldavite and suevite compositions. Our data indicate that the investigated samples are by-products of metallurgic activity. This conclusion is consistent with the presence in the Sigmaringen area of important cast iron furnaces which have been operating since the 18th century.