Three cleavage planes at right angles split it cleanly — break a chunk and it falls into stair-stepped cubic blocks, lead-gray with a bright metallic shine.
Fool's gold shows fine parallel grooves across its cube faces — a brassy, opaque tone that gold never has, with a greenish-black streak on the plate.
Dark grey to honey-brown with a glassy, almost tar-like sheen — under a loupe its faces glint resin-bright where galena would look flatly leaden.
Drag any sample across unglazed porcelain: galena leaves lead-gray, pyrite greenish-black, sphalerite pale brown — color on the rock lies, the streak does not.