Bornite is a mineral , sulfide of copper and iron (Cu 5 FeS 4 ). Named after the Czech mineralogist I. Born . Outdated synonyms - “mottled copper pyrite”, “copper purple”. It has two polymorphic modifications: the high-temperature (more than 228 ° C) modification is cubic- hexa - octahedral, and the low-temperature (less than 228 ° C) - tetragonal- scalenohedral.
| Bornite | |
|---|---|
 Bornite, skeleton crystal 7cm. Zhezkazgan , from http://mindraw.web.ru/ | |
| Formula | Cu 5 FeS 4 |
| Physical properties | |
| Colour | Copper Red, Indigo |
| Trait color | Dark gray to black |
| Shine | Metal |
| Transparency | Opaque |
| Hardness | 3–3.5 |
| Cleavage | Imperfect by (111) |
| Kink | Crustacean; fragile |
| Density | 4.9-5.3 g / cm³ |
| Syngonia | Rhombic , Cubic, Dodecahedral, Octahedral |
Content
Properties
The color is complex and is characterized by characteristic inconstancy: on a fresh fracture between bronze-yellow or copper-red to indigo-blue, over time it quickly changes to a mottled yellow-orange-red-blue due to the formation of an oxide film on the surface with a tarnish . Gloss metallic. Hardness 3 [1] . Very fragile. Density 4.9 - 5.3. Cleavage imperfect according to (110), kinky conch. Soluble in HNO 3 .
The chemical composition is variable. Theoretically, according to the chemical formula Cu 5 FeS 4 , it should be as follows: Cu - 63.3%, Fe - 11.2%, S - 25.5%. However, the composition of bornite varies significantly, since this mineral is able to contain chalcopyrite and chalcosine in the form of solid solutions.
Associated Minerals
Quartz , calcite , chalcosine , chalcopyrite , pyrite , enargite , magnetite , pyrrhotite, covellite.
Origin and deposits
Bornite can have both endogenous and exogenous origin. Bornite of endogenous origin is found in some medium and low temperature hydrothermal deposits. In some cases, it contains microscopic, usually lamellar inclusions of chalcopyrite. In paragenesis, in addition to chalcopyrite, there are: endogenous chalcosine, galena, sphalerite, pyrite, and others. Exogenous bornite is widely developed as the earliest secondary sulfide in the form of irregular veins, borders or continuous masses. Compared with other secondary sulfides, copper is less stable and easily degrades under weathering conditions.
Relatively rare, does not form large clusters. Usually in the form of impregnations or streaks in quartz or calcite in association with other copper sulfides. Also, individual, usually poorly formed, small crystals in voids and on the walls of cracks. Under near-surface conditions, it is unstable and is easily destroyed by weathering or turns into chalcosine and covellins . It is found in small amounts in many deposits of the Urals in the upper zones of secondary sulfide enrichment. Also, the Dzhezkazgan and Sayak deposits ( Kazakhstan ), Mansfeld copper shales ( Germany ), Lubin near Legnica, ( Poland ), Slovenia , Butte ( Montana , USA ), Tsumeb ( Namibia ).
Notes
- ↑ Bornite // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
Links
Literature
- Levinson-Lessing F. Yu. Bornit // Brockhaus and Efron Encyclopedic Dictionary : 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
- http://edu.tsu.ru/eor/resourse/803/html/291.html