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