spiegeleisen
A ferromanganese alloy containing approximately 15% manganese and small quantities of carbon and silicon.
countable, uncountable
Historically, spiegeleisen was the standard form in which manganese was traded and used in steelmaking.
Where it comes from
From German Spiegeleisen (literally “mirror iron”).
Adapted from the Wiktionary entry spiegeleisen (CC BY-SA 4.0).