Spiegel iron

CIDE DICTIONARY

Spiegel iron,  [G. spiegel mirror + E. iron.].

 A fusible white cast iron containing a large amount of carbon (from three and a half to six per cent) and some manganese. When the manganese reaches twenty-five per cent and upwards it has a granular structure, and constitutes the alloy ferro manganese, largely used in the manufacture of Bessemer steel. Called also specular pig iron, spiegel, and spiegeleisen.  [1913 Webster]