Editorial Feature

Bornite (Peacock Ore) – Occurrence, Properties, and Distribution

Sep 26 2013

Bornite was named after Ignaz Edler von Born (1742–1791), a distinguished Austrian mineralogist. This mineral is also referred to as peacock ore.

Properties of Bornite

The following are the key properties of bornite:

Cell Data
- Space group: Pbca
- a = 10.950
- b = 21.862
- c = 10.950
- Z = 16
Crystal Data
- Orthorhombic, pseudocubic
- Point group: 2/m2/m2/m
- Crystals pseudocubic, dodecahedral, octahedral, to 6 cm; commonly granular, compact, or massive, disseminated
- Twinning: On {111}; commonly shows penetration twins
- X-ray powder pattern: 1.937 (100), 3.18 (60), 2.74 (50), 1.258 (50), 1.119 (50), 3.31 (40), 2.50 (40)

Chemical Composition

Elements	Content 1	Content 2	Content 3
Cu	62.99	62.8	63.33
S	25.58	25.7	25.55
Fe	11.23	11.4	11.12
Pb	0.10	-	-
Total	99.90	99.9	100.00

Optical Properties
- Anisotropism: Weak
- 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
- Pleochroism: Weak but noticeable

Estimated Properties

Electron density	Bulk density (electron density) = 4.77 g/cm³ note: Specific gravity of bornite = 5.09 g/cm³
Photoelectric	PE_Bornite = 33.28 barns/electron U=PE_Bornite x ρ electron density= 158.63 barns/cm³
Fermion index	Fermion index = 0.0042761281 Boson index = 0.9957238719
Radioactivity	Bornite is not radioactive

How to Identify Bornite

Bornite can be identified in the field by its color variations of copper red, bronze brown and purple. Its opaque form has {111} imperfect cleavage. This mineral has a metallic luster with grayish black streak. The fracture on this mineral is conchoidal. The density of bornite is 4.9 - 5.3 g/cm³ with a hardness of 3 – approximate to calcite. It is non-fluorescent and magnetic after heating.

Global Distribution

Bornite is distributed in the following places:

USA - From Butte, Silver Bow Co., Montana, and at Bristol, Hartford Co., Connecticut
England - From the Carn Brea mine, Illogan, and elsewhere in Cornwall
Zimbabwe - Large crystals from the Mangula mine, Lomagundi district
Austria - From the Frossnitz Alpe, eastern Tirol
Kazakhstan - At Dzhezkazgan
Morocco - In the Nouva mine, Talate
USA - Magma mine, Superior, Pinal Co., and Bisbee, Cochise Co., Arizona; and Kennicott, Alaska
South Africa - At Ookiep, Namaqualand, Cape Province; and the Messina mine, Transvaal
Australia - From Mt. Lyell, Tasmania, and Olympic Dam, Roxby Downs, South Australia.

Occurrence of Bornite and Useful Mineral Association

Bornite is associated with, and disseminated in, mafic igneous rocks, pegmatites, medium-to high-temperature hydrothermal deposits, contact metamorphic skarn deposits and in sedimentary cupriferous shales.

It is often associated with minerals such as chalcopyrite, pyrite, other copper and iron sulfides, garnet, calcite, wollastonite, and quartz.