Pyrite

Pyrite, often called "Fools Gold", has a silvery-yellow to golden metallic color. It is very common and may occur in large crystals. It has been used by ancient civilizations as jewelry, but is hardly used nowadays. Pyrite is sometimes incorrectly known as Marcasite in the gemstone trade. Marcasite is mineral that is a polymorph of Pyrite, and can be fragile and unstable, and is not fit for gemstone use.

Color	Metallic, Yellow, Gray
Hardness	6Â -Â 6.5
Crystal System	Isometric
SG	4.9Â -Â 5.2
Transparency	Opaque
Double Refraction	None
Luster	Metallic
Cleavage	None
Mineral Class	Pyrite