What Is Pyrite? The Real Story Behind "Fool's Gold"

Pyrite is iron sulfide, and it earned the nickname "fool's gold" because its metallic golden luster fooled prospectors during gold rushes. Once you know what to check, though, telling them apart is straightforward: pyrite is brittle and shatters when struck, while real gold is malleable and dents instead; pyrite is also noticeably harder than gold on the Mohs scale, and often forms in sharp, striated cubic crystals — a shape gold rarely takes.

Interestingly, pyrite wasn't always entirely "foolish": some deposits genuinely contain trace amounts of real gold locked within their structure. Pyrite forms in a wide range of geological environments and is found worldwide; the striking cubic crystal specimens prized by collectors often come from Navajún, Spain, and from Peru.