elementCalxElementsThe powdery ash-like residue after strong heating of a metal or mineral. Not lime alone, and not ash from wood.Calx is used in Medicine.Pliny’s Natural History treats calx and burned earths among caustic and drying applications. A Roman-era pharmacological use of burned lime-earth, not quicklime as the fresh caustic already filed and not chalk as soft white earth.from Pliny the Elder · Natural History, c. 77 CEused in · sourced · documentedsourcesNatural History · Pliny the ElderPliny, Naturalis Historia.