You've probably heard of fool's gold, and it might make you think of prospectors in old timey California seeking their fortunes. But there's another kind of fool's gold called chalcopyrite, and lucky for those that want to strike...

So, rocks are hard. But the scale we use to rank them, the Mohs scale, is only really good at quantifying that for one kind of hardness, and topaz is a perfect stone to talk about to explain that. And you can check it out in our SciShow...

Dr. Forrester identifies five minerals.