1 Higgs: Look, Miss Wendy, I be findin’ this shiny yellow rock in Martinique.
2 Higgs: Be it gold?
3 Wendy: Nay, Bosun Higgs. That be fool’s gold. It be common all over this part o’ the world.
4 Wendy: We be callin’ it the pyrites o’ the Caribbean.

Honestly I've never really seen much resemblance between iron pyrite and gold. It's not really clear to me how someone - particularly someone who might be looking for gold and thus have a decent idea of its properties - could mistake one for the other.

As Wikipedia says: [Pyrite] is distinguishable from native gold by its hardness, brittleness and crystal form. Natural gold tends to be anhedral (irregularly shaped), whereas pyrite comes as either cubes or multifaceted crystals.

It seems like hardness, brittleness, and shape are plenty of clues to be able to tell the difference. I mean... you'd have to be some sort of fool to mistake one for the other.