Jacobite

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Jacobite
Jacobsite-772601.jpg
Black, octahedral scallop crystals on matrix from the N'Chwaning Mine II, Kuruman , South Africa (field of view 1.3 cm)
General and classification
other names

Magnetostibian

chemical formula
  • Mn 2+ Fe 3+ 2 O 4
  • (Mn 2+ , Fe 2+ , Mg) (Fe 3+ , Mn 3+ ) 2 O 4
Mineral class
(and possibly department) 		Oxides and hydroxides
Similar minerals Hercynite , magnetite and other minerals of the spinel group
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fd 3 m (No. 227)Template: room group / 227
Lattice parameters a  = 8.47  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 5.5 to 6.5 ( VHN 100 = 665 to 707)
Density (g / cm 3 ) measured: 4.76; calculated: 5.03
Cleavage is missing; possible secretions after {111}
Break ; Tenacity brittle
colour brownish black to black
Line color reddish black to brown
transparency opaque, translucent edges
shine Metallic gloss, semi-metallic gloss, matt
magnetism strong magnetic

Jacobite is a rather seldom occurring mineral from the mineral class of "oxides and hydroxides" with the idealized chemical composition Mn 2+ Fe 3+ 2 O 4 and is therefore chemically a manganese - iron - oxide .

Jacobite crystallizes in the cubic crystal system , but rarely develops octahedral crystals up to about 6 mm in size. It is usually found in the form of rounded inserts and granular to massive mineral aggregates or crusty coatings. The mineral is generally opaque and only translucent on thin crystal edges. The surfaces of the brownish-black to black crystals have a semi-metallic to metallic luster . In aggregate form, however, the surfaces are rather matt. The line color of Jakobsit differs from its surface color and varies between reddish black and brown.

With magnetite (Fe 2+ (Fe 3+ ) 2 O 4 ), Jakobsite forms a gapless mixed crystal row .

Etymology and history

Jakobsite was first discovered in the former Jakobsberg iron and manganese ore mine ( 59 ° 49 ′  N , 14 ° 6 ′  E ) about 2 km south of Nordmark in the Swedish municipality of Filipstad (Värmland). The first description was in 1869 by Augustin Alexis Damour , who named the mineral after its type locality .

The type material of the mineral is kept in the Naturhistoriska riksmuseet ( Natural History Museum ) in Stockholm .

classification

The current classification of the International Mineralogical Association (IMA) is one of the Jakobsit to spinel supergroup , where he together with chromite , Cochromit , Coulsonit , Cuprospinell , Franklinite , Gahnit , Galaxit , Hercynit , Magnesiochromite , Magnesiocoulsonit , Magnesioferrit , magnetite , Manganochromit , spinel , Trevorit , Vuorelainenit and Zincochromit forming the spinel subgroup within the Oxispinelle.

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , Jacobite belonged to the mineral class of "oxides and hydroxides" and there to the division of "oxides with a metal: oxygen ratio = 3: 4 (spinel type M 3 O 4 and related compounds) ", where together with cuprospinel , franklinite , magnesioferrite , magnetite and trevorite, the group of" ferrite spinels "with the system no. IV / B.02 formed.

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, also classifies Jakobsite in the oxides division with a substance 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 , hercynite , magnesiochromite , magnesiocoulsonite , magnesioferrite, magnetite, manganochromite , nichromite , 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 Jacobite to the class of "oxides and hydroxides" and there in the section "multiple oxides". Here it is in the " iron subgroup " with the system no. 07.02.02 to be found in the subsection “Multiple Oxides (A + B 2+ ) 2 X 4 , Spinel Group ”.

Chemism

The idealized chemical composition of Jakobsite is given as Mn 2+ Fe 3+ 2 O 4 . The analyzed samples from the Jakobsberg type locality in Sweden and from the Bald Knob site in Alleghany County of North Carolina (USA) showed, however, that a small proportion of divalent manganese (Mn 2+ ) is due to Fe 2+ and / or Mg and a smaller one Part of the trivalent iron (Fe 3+ ) can be replaced ( substituted ) by Mn 3+ . The chemical formula is therefore given in various sources with (Mn 2+ , Fe 2+ , Mg) (Fe 3+ , Mn 3+ ) 2 O 4 .

In addition, the samples had very low levels of aluminum and titanium , which, however, were not included in the mixed formula.

Crystal structure

Jakobsite crystallizes cubically in the space group Fd 3 m (space group no. 227) with the lattice parameter a  = 8.47  Å and eight formula units per unit cell . Template: room group / 227

Modifications and varieties

The compound Mn 2+ Fe 3+ 2 O 4 is dimorphic and occurs naturally as tetragonally crystallizing iwakiite in addition to the cubic crystallizing Jacobite .

A mineral described by Lars Johan Igelström (1822-1897) in 1894 and referred to as magnetostibian was initially classified as a very imprecisely known, complex antimony oxide after analyzes by Paul B. Moore and in 1973 regarded as identical to Jakobsite and discredited.

A mineral mix of Hausmannite and Jakobsite, the individual name Vredenburgite .

Education and Locations

Jakobsite (black, 6 mm large octahedron) with tiny garnets (orange) on a lizardite matrix (yellow coating) from the Wessels Mine, Hotazel , South Africa (size 5 cm × 4 cm × 3.25 cm)
Grainy mineral aggregate with a crust of Jacobite (black) and zincite (red) from the Franklin Mine, New Jersey, USA. The manganosite under the thin scallop crust is still unweathered green. (Size: 3.0cm × 2.0cm × 1.5cm)

Jacobite is formed either primarily or secondarily as a conversion product from other manganese-containing minerals in metamorphic manganese deposits . The accompanying minerals include hausmannite , galaxite , braunite , pyrolusite , coronadite , hematite and magnetite .

As a rather rare mineral formation, Jakobsite can sometimes be abundant at various sites, but overall it is not very common. A total of around 180 sites (as of 2018) have been documented for Jakobsit so far. In addition to its type locality , the Jakobsberg mine near Nordmark, the mineral could also be found in several places in the province of Värmland , including Långban and Pajsberg . Other well-known sites in Sweden are Garpenberg in the municipality of Hedemora and Ulvshyttan in the municipality of Ludvika (Dalarnas län), Kesebol in the municipality of Åmål (Västra Götalands län, formerly Dalsland) and Grythyttan in the municipality of Hällefors , several pits in the municipality of Lindesberg and the Häste-Erzfeld in the municipality of Norberg (Västmanland County).

In Germany, Jakobsite appeared, among other things, in rock samples from the rhyolite quarry Fuchs on the Hartkoppe near Sailauf in Bavaria, which is also considered a type locality for the minerals Sailaufit and Okruschit . Further Jacobite finds were from the Fischbacher works in the Altenkirchen district and at the Krufter oven, at several locations near Mendig (In den Dellen, Thelenberg, Wingertsberg) and at Ettringer Bellerberg in the Mayen-Koblenz district in Rhineland-Palatinate and from shaft 139 ( Abrahamhalde) near Lauta in the Saxon Erzgebirgskreis.

In Austria, the mineral was found, among other things, in rock samples that arose when the wall for the Mooserboden reservoir was built . On the slopes east of the dam, the prasinites present there are traversed by manganese-rich veins , two of which were cut when the dam was built in the 1950s. Jakobsite is also known from a radiolarite bite on the Fuchsalm in the Taurach Valley, also in Salzburg . Two other well-known sites are manganese mineralization on Friedlkogel near Veitsch in Styria as well as in Ködnitztal and on the Wunspitze in Tyrol.

In Switzerland, Jakobsit has so far been found at Ausserferrera and Le Prese in the canton of Graubünden , in the municipality of Sargans in the canton of St. Gallen and at Pipjitälli near the Pipji glacier and in the Täschtal , part of the Mattertal in the canton of Valais.

Other previously known sites are in Australia, Brazil, China, France, Ghana, India, Israel, Italy, Japan, Canada, Kazakhstan, Kenya, Morocco, the Republic of Macedonia, Mexico, Mongolia, Namibia, Norway, Romania, Russia , Slovakia, Spain, South Africa, Sudan, Tanzania, Turkey, the Czech Republic, the United Kingdom (UK) and the United States of America (USA).

use

Due to the local accumulation on Jakobsberg in Wermland, Jakobsite was mined as manganese ore.

See also

literature

  • AA Damour : Notice sur la jakobsite, nouvelle espèce minérale . In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences . tape 69 , 1869, pp. 168–172 (French, rruff.info [PDF; 253 kB ; accessed on August 3, 2018]).
  • K. Johansson: IV. Mineralogical communications. 4. Jacobsite . In: Journal of Crystallography . tape 68 , 1928, pp. 87–118 ( rruff.info [PDF; 1.9 MB ; accessed on August 3, 2018] Jacobsit from p. 21).
  • Michael Fleischer : New Mineral Names . In: American Mineralogist . tape 29 , 1944, pp. 73–74 ( rruff.info [PDF; 106 kB ; accessed on August 5, 2018]).
  • Michael Fleischer : New Mineral Names . In: American Mineralogist . tape 58 , 1973, p. 560–562 ( rruff.info [PDF; 349 kB ; accessed on August 5, 2018]).

Web links

Commons : Jakobsit  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  505 (first edition: 1891).
  2. ↑ a b c d 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 (English).
  3. ↑ a b IMA / CNMNC List of Mineral Names; March 2018 (PDF 1.65 MB)
  4. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  5. ↑ a b c d e f g h i j Jacobsite . 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; 69  kB ; accessed on August 3, 2018]).
  6. ↑ Mindat - Jacobsite (English)
  7. ↑ 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 ( preliminary version online [PDF]).
  8. ^ Karl Hugo Strunz , Christel Tennyson : Mineralogical tables . 4th edition. Academic publishing company Geest & Portig KG, Leipzig 1966, p.  176 ( geokniga.org [PDF; 29.5 MB ; accessed on August 5, 2018]).
  9. ↑ Michael Fleischer : New Mineral Names . In: American Mineralogist . tape  58 , 1973, p. 560–562 ( rruff.info [PDF; 349 kB ; accessed on August 5, 2018]).
  10. ↑ Mindat - Vredenburgite (English)
  11. ↑ Mindat - description of the location of Mooser dam, Mooserboden reservoir, Kaprun valley, Hohe Tauern, Salzburg, Austria
  12. ↑ List of localities for Jakobsite in the Mineralienatlas and Mindat