Geological Fun Fact

Pyrite is often called "fool's gold" because it looks like gold, but isn't. It doesn't look exactly like gold, it's a bit more of a silver-y colour than gold itself is, and pyrite forms cubes while gold very much doesn't, but it's still a mistake that's possible to make*.

Guess what mineral is hilariously common in gold deposits?

Yep. Pyrite.**

*I spent a fair amount of time staring at a rock that was being used as way to teach us the difference in appearance between gold and pyrite, and I just couldn't find any and it was so confusing-- until it was pointed out that I was just looking at the pyrite. [Facepalm].

**There is an actual geological reason! Gold is transported in hydrothermal (and other) fluids as Au(HS)2, which can react with iron oxide (FeO) to form pyrite (FeS2), hydrogen and insoluble chunks of gold. Which means you tend to find gold and pyrite together.