Geleisen

Geleisen is a historical term used in German-language metallurgy to describe iron or iron-containing material with a yellowish coloration. The term literally means yellow iron and its precise meaning varied by region and period, lacking a single formal definition in modern practice.

In older technical literature, Geleisen could denote pig iron produced from certain ore blends or cast iron with a distinctive surface coloration, sometimes attributed to oxide coatings or specific impurity contents. The yellow hue was often linked to the presence of particular iron oxides or ore impurities like limonite, though the exact cause was not standardized.

Because the concept was descriptive rather than classificatory, Geleisen did not correspond to a fixed chemical composition or mechanical specification. Different sources might ascribe different properties to Geleisen, ranging from casting behavior to ductility, depending on local processing methods and ore sources. The term thus served as a practical label in archival texts rather than a controlled metallurgical category.

In contemporary metallurgy, Geleisen is largely obsolete. Modern practice uses standardized categories based on form and composition, such as pig iron, cast iron, gray iron, white iron, ductile iron, and various steel classifications. The term remains of interest primarily for historical study, especially when interpreting older manufacturing records, mining reports, or engineering treatises that reference yellow-colored iron artifacts or materials.

See also: pig iron, cast iron, gray iron, white iron, ductile iron, metallurgy, historical terminology.