Spiegel iron \Spie"gel i`ron\ [G. spiegel mirror + E. iron.]

(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.

Source: Webster's Revised Unabridged Dictionary (1913)