Hercynite
| Hercynite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | FeAl 2 O 4 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.BB.05 ( 8th edition : IV / B.01) 02/07/01/03 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | Fd 3 m (No. 227) |
| Lattice parameters | a = 8.13 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | 7.5 to 8 |
| Density (g / cm 3 ) | measured: 4.40; calculated: [4.26] |
| Cleavage | indistinct; Secretions after {111} possible |
| Break ; Tenacity | shell-like |
| colour | dark green to black |
| Line color | dark gray green to dark green |
| transparency | opaque, translucent in thin edges |
| shine | Glass gloss |
| Crystal optics | |
| Refractive index | n = 1.80 to 1.83 |
| Birefringence | none, as it is optically isotropic |
Hercynite or Ferrospinell is a rather seldom occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the cubic crystal system with the chemical composition FeAl 2 O 4 and structurally belongs to the group of spinels .
Hercynite only develops microscopic crystals with an octahedral habit and a glass-like sheen . It is usually found in the form of granular to massive mineral aggregates from dark green to black in color with dark gray-green to dark green streak color . The mineral is generally opaque and only translucent on thin crystal edges.
Similar to the other spinels, Hercynite has a high Mohs hardness of 7.5 to 8 and is therefore able to scratch window glass or to grind optical glasses or mirrors as emery .
Etymology and history
Was first discovered in a Hercynit pegmatite - deposit near the West Bohemia town Poběžovice (German: Ronsperg ) in the foothills of Oberpfälzer forest in the Czech Republic. It was described in 1839 by Franz Xaver Zippe , who named the mineral in his own words based on the Latin name of the Bohemian Forest Silva Hercynia . In the original meaning, however, the Romans marked Hercynia generally the forest areas from the Alps to the resin and Hercynia silva called Hercynian forest , a mountain range north of the Danube located east of the Rhine.
classification
The current classification of the International Mineralogical Association (IMA) is one of the Hercynit to spinel supergroup , where he together with chromite , Cochromit , Coulsonit , Cuprospinell , Franklinite , Gahnit , Galaxit , Jakobsit , Magnesiochromite , Magnesiocoulsonit , Magnesioferrit , magnetite , Manganochromit , spinel , Trevorit , Vuorelainenit and Zincochromit forming the spinel subgroup within the Oxispinelle.
Already in the now outdated, but still common 8th edition of the mineral classification according to Strunz , the hercynite belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with the molar ratio of metal: oxygen = 3: 4 (spinel type M 3 O 4 and related compounds) ”, where together with gahnite, galaxite and spinel he created the group of“ aluminate spinels ”with system no. IV / B.01 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies Hercynite in the division of "Oxides with the molar ratio of metal: oxygen = 3: 4 and comparable". This, however, is further divided according to the relative size of the participating cations , so that the mineral according to its composition in the subdivision to find "With only medium-sized cations" where it along with Brunogeierit , chromite, Cochromit, Coulsonit, Cuprospinell, Filipstadit , Franklinite , Gahnite, galaxite, jacobsite, magnesiochromite, magnesiocoulsonite, magnesioferrite, magnetite, manganochromite, nichromite (N), qandilite , spinel, trevorite, ulvöspinell , vuorelainenite and zincochromite the "spinel group" with the system no. 4.BB.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns hercynite to the class of "oxides and hydroxides" and there in the category of "multiple oxides". Here it is together with spinel, galaxite and gahnite in the "aluminum subgroup" with system no. 07.02.01 to be found in the subsection “ Multiple oxides (A + B 2+ ) 2 X 4 , spinel group ”.
Crystal structure
Hercynite crystallizes cubically in the space group Fd 3 m (space group no. 227) with the lattice parameter a = 8.13 Å and 8 formula units per unit cell .
Education and Locations
Hercynite forms as a by- product in intramagmatic magnetite and titanomagnetite deposits as well as in granulites and other crystalline slates . In addition to magnetite, andalusite , corundum , ilmenite and sillimanite occur as accompanying minerals .
As a rather rare mineral formation, Hercynite can sometimes be abundant at various sites, but overall it is not very common. Around 300 sites are known to date (as of 2012). In addition to its type locality Poběžovice, the mineral appeared in the Czech Republic in many other places in Bohemia and in some places in Moravia .
In Germany, Hercynite has so far been found mainly in the Eifel in Rhineland-Palatinate, but has also occurred at some sites in Baden-Württemberg ( Sasbach ), Bavaria ( Maroldsweisach , Bodenmais , Waldeck ), Hesse, Lower Saxony, North Rhine-Westphalia and Saxony ( Löbauer Berg ).
In Austria, the mineral was found at Pauliberg in Burgenland, near Kollnitz / Sankt Paul in Lavanttal in Carinthia, in several places in the Dunkelsteinerwald (Lower Austria), in the Leckbachgraben in the Habach Valley and near Strobl in Salzburg, near Luftenberg on the Danube in Upper Austria as well near Kapfenstein , Klausen / Bad Gleichenberg and Klöch in Styria.
In Switzerland, Hercynite has so far only been found in the Canton of Graubünden , more precisely on the Wolfgang Pass and in Val Forno near Bregaglia .
Other sites are found in Egypt, Algeria, the 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, Hungary, the United Kingdom and the United United States of America.
Hercynite could also be detected in rock samples from the east Pacific ridge as well as outside the earth on the moon .
See also
literature
- FXM Zippe : About the Hercinite, a previously unknown species of the mineral kingdom . In: Negotiations of the Society of the Fatherland Museum in Bohemia, 17th hearing . 1839, p. 19–27 ( rruff.info [PDF; 800 kB ; accessed on September 1, 2018]).
Web links
- Mineral Atlas: Hercynite (Wiki)
- Database-of-Raman-spectroscopy - Hercynite (English)
- Webmineral - Hercynite (English)
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 188 .
- ↑ a b c d Hercynite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 110 kB ; accessed on September 1, 2018]).
- ↑ FXM Zippe : About the Hercinite, a previously unknown species of the mineral kingdom . In: Negotiations of the Society of the Fatherland Museum in Bohemia, 17th hearing . 1839, p. 19–27 ( rruff.info [PDF; 800 kB ; accessed on September 1, 2018]).
- ↑ Cristian Biagioni, Marco Pasero: The systematics of the spinel-type minerals: An overview . In: American Mineralogist . tape 99 , no. 7 , 2014, p. 1254–1264 , doi : 10.2138 / am.2014.4816 (English, preliminary version online [PDF]).
- ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 358-359 .
- ↑ Mindat - Hercynite (English)
- ↑ a b Mindat - localities for Hercynite