Geological curios
Pyrite (fool's gold)
Bright brassy cubes and clusters that fooled prospectors for centuries. In creek gravel it forms when iron-rich groundwater meets the sulfur left behind by decaying organic matter — which is why pyrite often replaces fossils, preserving belemnites and shells in metallic gold.
How to spot it
- ▸Brassy yellow with a metallic sheen — much harder than real gold
- ▸Often crystallized as cubes with squared edges
- ▸Streak (rub on unglazed porcelain) is greenish-black, not gold
- ▸Brittle — breaks rather than bends; real gold deforms under a knife edge
- ▸Pyritized fossils are bonus finds — same shape as belemnites or shells but solid metal
Easy to confuse with
- ·Chalcopyrite (more brassy, often iridescent)
- ·Mica (flaky, flexible — pyrite never bends)
- ·Real gold (much rarer, much softer — dents under a knife)
Reported at these sites
About the category
Mineral curios — pyrite, amber, agates, concretions — that ride along in the same gravel as the fossils.