[mass noun] An alloy of iron and manganese, used in steel-making.
- ‘In 1904, Palmerton would begin producing spiegeleisen, taking advantage of the residuum from the zinc oxide furnaces.’
- ‘The quality of the steel produced would be poor if it absorbed too much oxygen and too little carbon so spiegeleisen, a triple compound of iron, manganese and carbon was added (manganese combines readily with oxygen).’
- ‘Realising the enormous value of his discovery he continued with his experiments to master the facts concerning spiegeleisen when alloyed in various ways.’
Mid 19th century: from German, from Spiegel mirror + Eisen iron.