The Collaborative International Dictionary of English v.0.48:
Calx \Calx\, n.; pl. E. Calxes, L. Calces. [L. Calx, calcis.
limestone; cf. Gr. ? gravel. ?, ?, pebble, Skr. ? gravel, Ir.
carraic rock Gael. carraig, W. careg, stone. Cf. Chalk.]
(a) Quicklime. [Obs.]
(b) 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
Note: Metallic calxes are now called oxides.
2. Broken and refuse glass, returned to the post.