Digenite
- α - chalcocite
- Blue isotropic chalcocite
Digenite, outdated also known as α - chalcocite or Blue isotropic chalcocite, is a mineral from the mineral class of " sulfides and sulfosalts ," which can be abundant in various localities in part, but overall is not widespread. It crystallizes in the trigonal crystal system with the chemical composition Cu9S5 or β - Cu1, 8S and is found mostly in the form of adhesions with other copper sulphides and massive mineral aggregates, but rarely in the form of trigonal or pseudocubic crystals to about 3 cm size of blue-black color with gray black stroke color.
Digenite is opaque even in thin layers. In the crystal faces fresh samples or on fresh cut or broken surfaces shows strong metallic luster. However, these plates run in the air after some time in black and matt or form a brown, powdery coating.
Special Features
Before the blowpipe Digenite melt splashing in a brittle ball and using soda easily obtained a copper grain. In nitric acid dissolves Digenite with separation of sulfur and color the liquid green.
Etymology and history
Was first discovered Digenite at Sangerhausen in Saxony- Anhalt and described in 1844 by August Breithaupt, of the mineral due to its chemical affinity with chalcocite and covellite after the Greek words δύο [ DYO ] or its prefix δι [di ] for two- and γένος [ genos ] of species, genus, family, or tribe - a combination that is " twofold descent" - named.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Digenite belonged to the mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium > 1: 1 " where he formed a distinct group with Anilith, chalcocite, Djurleit, Geerit, Roxbyit, Spionkopit and Yarrowit.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Digenite also in the class of " sulfides and sulfosalts " and there in the department of "Metal Sulfides, M: S> 1: 1 ( mainly 2: 1) " a. This division, however, is further subdivided according to the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subdivision " with copper ( Cu), silver (Ag ) and / or gold ( Au) " is to find where it together with the so far only known mineral hypothetical high - digenite is the unnamed group 2.BA.05e.
The mainly common in English-speaking classification of minerals according to Dana assigns the digenite in the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is with chalcocite, Djurleit, Roxbyit, Anilith, Geerit and Spionkopit in the " Chalkosingruppe (Formula: Cu 2 -x S) " with the system no. 02:04:07 within the subdivision " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 2: 1" to find.
Education and Locations
Digenite formed by hydrothermal processes in primary or secondary copper deposits. Accompanying minerals are next to the chalcocite among others still Djurleit, bornite, chalcopyrite and other copper minerals and pyrite.
Overall, Digenite so far (as of 2011) are detected in more than 700 localities. Apart from its type locality Sangerhausen the mineral in Germany was still in many places in the Black Forest in Baden- Württemberg; at Hagendorf in the Upper Palatinate Forest and Wölsendorf district Schwandorf in Bavaria; at the Hohenstein in Hesse; in mouse Bach ( Stolberg ), Untermaubach and Eiserfeld in North Rhine -Westphalia; at low Hausen an der Appel, Kruft, Mendig, on Ettringer Bellerberg, Bleialf, Fischbach, Imsbach, Rammelsbach and Obermoschel in Rhineland -Palatinate; at Kastel and Walhausen in Saarland; at Neudorf ( Harzgerode ) and Mansfeld in Saxony -Anhalt and in Gera, Saalfeld and Schnellbach ( flea Seligenthal ) in Thuringia.
In Austria, the mineral appeared primarily in Carinthia, Lower Austria, Salzburg, Styria and Tyrol.
In Switzerland, they found Digenite among others Riniken in the canton of Aargau, Aranno in Ticino and in several places in the canton of Grisons.
Other localities are Argentina, Armenia, Australia, Belgium, Bolivia, Brazil, Bulgaria, Chile, China, the Democratic Republic of Congo, Ecuador, Eritrea, Fiji, Finland, France, Ghana, Greece, Greenland, Haiti, India, Indonesia, Iran, Ireland, Italy, Japan, Canada, Kazakhstan, Luxembourg, Madagascar, Mexico, Morocco, Myanmar, Namibia, New Zealand, Niger, Norway, Panama, Papua New Guinea, Peru, Philippines, Poland, Portugal, Romania, Russia, Zambia, Sweden, Serbia, Zimbabwe, Slovakia, Slovenia, Spain, South Africa, South Korea, Thailand, Trinidad and Tobago, Turkey, Hungary, Uzbekistan, the United Kingdom ( UK), the United States of America ( USA) and Cyprus.
Even in rock samples from the Mid-Atlantic Ridge, the Central Indian ridge and the East Pacific Rise Digenite could be detected.
Crystal structure
Digenite trigonal crystallized in the space group R3m ( Raumgruppen-Nr. 166) with the lattice parameters a = 3.92 Å and c = 48.00 Å and 15 formula units per unit cell.