Pyrite
Also known as '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.
Mineral formula: FeS2
Note marcasite is also FeS2; it crystallizes in the orthorhombic system.
Mineral group: member of the Pyrite group
Crystal system: isometric
Crystal habit: Typically cubic or pyritohedral (pentagonal dodecahedral), sometimes octahedral and combinations are common, resulting in striated faces. Most commonly pyrite is massive, granular, and sometimes radiating, reniform, discoidal or globular.
Cleavage: poor to indistinct on {001}.
Fracture: irregular / uneven, conchoidal
Color: pale brass-yellow
Luster: metallic
Diaphaneity: opaque
Moh’s scale hardness: 6 – 6 ½
Streak: greenish-black
Specific gravity: 4.8 - 5
Named after: the Greek "pyr" for "fire", because sparks flew from it when struck with another mineral or metal. Known to Dioscorides (~50 CE) under the name "περι υληζ ιατρικηζ" which included both pyrite and chalcopyrite.
Geological occurrence: Common in many rock types, igneous, metamorphic and sedimentary.
Energetic properties: According to Melody (2008) pyrite is a stone of protection and of self-confidence