calx

/kælks/
noun
  1. A powdery substance left after a metal or mineral has been heated strongly, especially calcium oxide (lime).
    • The ancient process of making cement involved burning limestone to create calx.
    • In chemistry class, they heated limestone to produce calx, or quicklime.
    • The blacksmith scraped the calx from the heated iron before shaping it.
Synonyms
What does "calx" mean? | whatsthatwordmean | whatsthatwordmean