Pyrite
(Fool's Gold)

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Pyrite is a very common mineral, found in a wide variety of geological formations from sedimentary deposits to hydrothermal veins and as a constituent of metamorphic rocks. The brassy-yellow metallic color of pyrite has in many cases lead to people mistaking it for Gold, hence the common nickname 'Fool's gold'.

Pyrite is quite easy to distinguish from gold: pyrite is much lighter, but harder than gold and cannot be scratched with a fingernail or pocket knife.