Hercynite
- Hercinit
- Ferrospinell
Hercynite or Ferrospinell is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in a cubic crystal system having a chemical composition FeAl2O4 and belongs structurally to the group of spinels.
Hercynite developed only microscopic crystals with octahedral habit and glass-like shine. He usually can be found in the form of granular to massive mineral aggregates. The mineral is generally opaque and dark green to black in color with dark gray-green to dark green line color. Thin crystal edges are allergings translucent.
Similar to the other spinels also has the hercynite a high Mohs hardness 7.5 to 8 and is thus able to scratch or grind as emery optical glass or mirror glass window.
Etymology and history
Was first discovered hercynite in the pegmatite deposits near the West Bohemian town Poběžovice ( German: Ronsperg ) in the foothills of the Upper Palatinate Forest in the Czech Republic. He was described in 1839 by Franz Xaver Zippe, who named the mineral in his own words from the latin name of the Bohemian Forest Silva Hercynia. In the original meaning, however, the Romans designated Hercynia general forest areas from the Alps to the resin and with Hercynia silva the so-called Hercynian forest, a mountain range located north of the Danube east of the Rhine.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the hercynite belonged to the department of " oxides with the molar ratio of metal: oxygen = 3: 4 ( spinel M3O4 and related compounds ) ," where he and along with gahnite, galaxite spinel, the group of " aluminate spinels " with the system no. IV/B.01 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the hercynite also in the department of " oxides with the molar ratio of metal: oxygen = 3: 4 and comparable " one. However, this is further divided according to the relative size of the cations involved, so that the mineral is "With only medium-sized cations " to find according to its composition in the subdivision where it together with Brunogeierit, chromite, Cochromit, Coulsonit, Cuprospinell, Filipstadit, Franklinite, gahnite, galaxite, Jakobsit, Magnesiochromite, Magnesiocoulsonit, Magnesioferrit, magnetite, Manganochromit, Nichromit, Qandilit, spinel, Tegengrenit, Trevorit, Ulvöspinell, Vuorelainenit and Zincochromit the " spinel group " with the system no. 4.BB.05 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the hercynite in the class of " oxides and hydroxides ," there but in the department of " multiple oxides " one. Here he is with spinel, gahnite galaxite and in the " aluminum sub- group " with the system no. 07:02:01 within the subdivision " Multiple oxides ( A B2 ) 2X4, spinel group " to find.
Education and Locations
Hercynite formed as Nebengemengteil in intra magmatic magnetite and titanomagnetite deposits and in granulites and other crystalline schists. Accompanying minerals occur in addition to the magnetite on, you still andalusite, corundum, ilmenite and sillimanite.
As a rather rare mineral hercynite formation can indeed be abundant in part to different sites, overall it is not very common. About 300 localities are so far (as of 2012) to be known. Apart from its type locality Poběžovice the mineral still occurred in many other places in Bohemia and in some places in Moravia in the Czech Republic.
In Germany hercynite has so far been mainly detected in the Eifel region of Rhineland -Palatinate, but also went to some discovery locations in Baden- Württemberg ( Sasbach ), Bavaria ( Maroldsweisach, ground corn, Waldeck ), Hesse, Lower Saxony, North Rhine -Westphalia and Saxony ( Löbauer mountain ) on.
In Austria, the mineral, among other things found on Pauliberg in Burgenland, in Kollnitz / Saint Paul in the Lavant valley in Carinthia, at several points in Dunkelsteinerwald (Lower Austria ), in the leak Bachgraben in Habachtal and Strobl, Salzburg, at Luftenberg on the Danube in Upper Austria and at Kapfenstein, Klausen / Bad Gleichenberg and Klöch in Styria.
In Switzerland Hercynite could be found so far only in the canton of Grisons, more precisely at the Wolfgang Pass and Val Forno Bregaglia.
Other localities lie among other things in Egypt, Algeria, Antarctic, Argentina, Ethiopia, Australia, Brazil, Chile, China, Finland, France, Greenland, India, Indonesia, Israel, Italy, Japan, Cambodia, Canada, Kazakhstan, Korea, Cuba, Lesotho, Madagascar, Morocco, New Zealand, Norway, Oman, Peru, Poland, Romania, Russia, Sweden, Slovakia, Spain, Sri Lanka, South Africa, Taiwan, Tajikistan, Tanzania, Uganda, Ukraine, the United Kingdom and the United States of America.
Even in rock samples from the East Pacific Rise and outside the earth on the moon Hercynite could be detected.
Crystal structure
Hercynite crystallized cubic space group Fd3m ( Raumgruppen-Nr. 227 ) with the lattice parameters a = 8.13 Å, and eight formula units per unit cell.