Bornite

Formula	Cu5FeS4
Origin	Dscheskazgan (Kazakhstan)
Description	black bornite crystals
Classification (Lapis)	Sulfides
Crystal System	Orthorhombic
Hardness	3,0 – 3,5
Colour	Copper-red to pinchbeck-brown on fresh surfaces, rapidly tarnishes iridescent purplish; in polished section, pinkish brown when fresh
Streak	Pale grayish black
Luminescence	none observed
Lustre	Metallic
Transparency (Opacity)	Opaque
Cleavage	in traces
Fracture	Uneven to subconchoidal
Magnetism
Geological Setting	Associated with and disseminated in mafic igneous rocks, in contact metamorphic skarn deposits, in pegmatites, in medium- to high-temperature hydrothermal deposits, and in sedimentary cupriferous shales; stable below ∼200 ◦C
Specific Gravity	5,07 g/cm3