Spiegeleisen (— mirror or specular; Eisen—iron)'s a ferromanganese alloy containing approximately 15% manganese and small quantities of carbon and silicon. Historically, this was the standard form in which manganese was traded and used in steel making (see Bessemer process); today, manganese's usually traded and used in more concentrated form, 80% manganese content being typical. Spiegeleisen's sometimes also referred to as specular pig iron, Spiegel iron, just Spiegel, or Bisalloy.… (More on Spiegeleisen)