Bornite
Current inventory:  0 gems
 

  
Bornite has been known since 1725, but not given its current name until 1845 when it was named for Ignaz Edler von Born (1742-1791), Austrian mineralogist.

Discovered in 1725;   IMA status: Valid (IMA approved 1962)

Chemistry

Chemical Formula:

Cu₅FeS₄

Copper Iron Sulfide

Molecular Weight:

501.84 gm

Composition:

Iron

11.13 %

Fe

Copper

63.31 %

Cu

Sulfur

25.56 %

S

100.00 %

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/B.02-30

Nickel-Strunz 10th Ed. ID:

2.BA.15

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
A : With Cu, Ag, Au

Related to:

n/a

Members of Group:

Argentiferous Bornite

Varieties:

Bornite (of Haidinger), Chalcomiklite, Erubescite, Lefverslag, Peacock Ore, Phillipsine, Phillipsite (of Beudant), Poikilite, Purple Copper, Purple Copper Ore, Variegated Copper, Variegated Copper Ore

Synonyms:

Bornite (of Haidinger), Chalcomiklite, Erubescite, IMA1962-s.p., Lefverslag, Peacock Ore, Phillipsine, Phillipsite (of Beudant), Poikilite, Purple Copper, Purple Copper Ore, Variegated Copper, Variegated Copper Ore

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals pseudocubic, dodecahedral, octahedral, to 6 cm; commonly granular, compact, or massive, disseminated.

Twinning:

On {111}; commonly shows penetration twins

Physical Properties

Cleavage:

Poor/Indistinct; in traces on [111]

Fracture:

Irregular/Uneven, Conchoidal, Subconshoidal

Tenacity:

Brittle

Moh's Hardness:

3.0 - 3.25

Density:

5.06 - 5.09 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Magnetic after heating

Optical Properties

Color:

Copper Red, Bronze Brown; tarnishing to an iridescent purplish surface after exposure to air and moisture

Transparency:

Opaque

Luster:

Metallic

Refractive Index:

R: (400) 19.9, (420) 18.8, (440) 17.9, (460) 17.6, (480) 18.0, (500) 18.8, (520) 20.0, (540) 21.3, (560) 22.9, (580) 24.4, (600) 26.0, (620) 27.5, (640) 28.8, (660) 30.2, (680) 31.6, (700) 32.7

Birefringence:

None (opaque)

Dispersion:

None

Pleochroism:

Weak but noticeable

Anisotrophism:

Weak; Color in reflected light: Brown, Pinkish

Occurances

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.

Common Associations:

Calcite, Chalcopyrite, Garnet, Pyrite, Quartz, Wollastonite, other copper and iron sulfides

Common Impurities:

Ag, Ge, Bi, In, Pb

Type Locality:

Jáchymov (St Joachimsthal), Ostrov, Krušné Hory Mts (Erzgebirge), Karlovy Vary Region, Bohemia (Böhmen; Boehmen), Czech Republic

Year Discovered:

1725 (IMA approved 1962)

View mineral photos:

Bornite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Bornite is a popular mineral for collecting but rarely available as a faceted gem. It is typically found as massive, opaque, metallic material that has a copper-red color on fresh exposures which quickly tarnish to an iridescent purple after exposure to air and moisture. Bornite may be confused with tarnished Chalcopyrite.

Bornite is an important copper ore mineral along with other copper ores such as Chalcopyrite, Covellite, Cuprite, Digenite and Tetrahedrite. Good crystals are rare and so Bornite is commonly known simply as a massive mineral ore. It is popular among children in souvenir shops where it is often sold as "peacock ore" or "peacock copper" because of its colorful iridescent tarnish. The colors are from an iridescent tarnish that forms on Bornite upon exposure to air. The tarnish is made of assorted copper oxides or hydroxides that form a very thin layer over the Bornite. In the case of Bornite, the tarnish will have a purplish, violet or blue color. Because Bornite is often intergrown with Chalcopyrite which tarnishes to more greens and yellows, the peacock ore may have many colors ranging from purple to blue to green to yellow.

Important localities for fine crystals include: in the USA, from Butte, Silver Bow County, Montana, and at Bristol, Hartford County, Connecticut. In England, from the Carn Brea mine, Illogan, and elsewhere in Cornwall. Large crystals from the Mangula mine, Lomagundi district, Zimbabwe. From the Frossnitz Alpe, eastern Tirol, Austria. At Dzhezkazgan, Kazakhstan. In the N’ouva mine, Talate, Morocco.
 

  
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