How do you tell if gold is fake?

How do you tell if gold is fake?
With jewelry, look for the markings- and understand that 14K Gold and 14K HGE is not the same thing. For unmarked jewelry, a jeweler may use the "acid test", where an item is brushed against a dark surface (leaving a minute streak of gold- and different strength acids used to dissolve the gold. There are also electronic test instruments. When prospecting, gold is EXTREMELY heavy- it is soft and not brittle, and nothing that glitters is gold.