Chemical composition -- Iron sulfide crystallized in the isometric (cubic) system. Often confused with marcasite, an orthorhombic form of iron sulfide..
Color -- Brassy yellow. Sometimes shows an iridescent tarnish due to oxidation.
Optics -- Opaque, metallic luster.
Durability -- Hardness 6-6.5.
Crystal structure -- Isometric (cubic).
Specific Gravity -- 5.0.
Sources -- Numerous sources throughout the world. Sometimes used in inexpensive jewelry, often as faceted rose cuts.