Emily Dickinson Lexicon

WACK'E, or WACK'Y, n.

A rock nearly allied to basalt, of which it may be regarded as a more soft and earthy variety. Its color is a greenish gray, brown or black. It is opake, yields easily to the knife, and has a greasy feel. Its principal ingredient is silex. Gray wacky is a different species of rock, being a kind of sandstone. – Cyc. Wacky is a mineral substance intermediate between clay and basalt. – Ure.