"Lime" that is neither quicklime (calcium oxide) nor caustic lime (calcium hydroxide) refers to calcium carbonate. Calx, however, can also refer to any calcined metal, which is a metal that has been oxidized.

In practical terms, the "calx" of an anion will refer to a salt with a calcium cation, while the "calx" of a cation (any metal) will refer to a metallic oxide.

for example, Calx of Tartar is calcium tartrate, while Calx of Copper is cuprous oxide.