Webster's Revised Unabridged Dictionary · 1913

Calx

Calx , noun

[Latin Calx, calcis. limestone; compare Greek {not transcribed} gravel. {not transcribed}, {not transcribed}, pebble, Sanskrit {not transcribed} gravel, Ir. carraic rock Gael. carraig, Welsh careg, stone. Compare Chalk.]

1.
(a) (Chemistry) Quicklime.
(b)
(Chemistry) The substance which remains when a metal or mineral has been subjected to calcination or combustion by heat, and which is, or may be, reduced to a fine powder. [Obsolete]

Metallic calxes are now called oxides.

2.
Broken and refuse glass, returned to the post.