spiegel iron

Wiktionary

1. n. spiegeleisen

GNU Webster's 1913

1. (Metal.) 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.

WordNet 3.0

1. n. pig iron containing manganese; used as a deoxidizing agent and to raise the manganese content in making steel