Humboldtin

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Humboldtin
Humboldtine.jpg
Humboldtin from the "Csordakúti Mine", Bicske -Csordakút, Fejér County , Hungary (size: 0.75 "× 0.75"; corresponds to 1.9 cm × 1.9 cm)
General and classification
other names
  • Iron oxalate
  • Oxalite
  • Oxalate iron
chemical formula FeC 2 O 4 · 2H 2 O
Mineral class
(and possibly department) 		Organic compounds / oxalates
System no. to Strunz
and to Dana 		10.AB.05 ( 8th edition : IX / A.01)
50.01.03.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 12.011  Å ; b  = 5.557 Å; c  = 9.920 Å
β  = 128.53 °
Formula units Z  = 4
Frequent crystal faces {100}, {001}, {110}, {101}
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) measured: 2.28; calculated: 2.307
Cleavage perfect according to {110}, imperfect according to {100} and {010}
Break ; Tenacity uneven
colour yellow to brownish yellow (amber yellow)
Line color light yellow
transparency transparent to opaque
shine Resin gloss to matt
Crystal optics
Refractive indices n α  = 1.494
n β  = 1.561
n γ  = 1.692
Birefringence δ = 0.198
Optical character biaxial positive
Pleochroism visible:
X = very light yellowish green
Y = light greenish yellow
Z = strong yellow
Other properties
Chemical behavior soluble in acids; poorly soluble in water

Humboldtin is a rarely occurring mineral from the mineral class of " organic compounds " with the chemical composition FeC 2 O 4 · 2H 2 O and is therefore a water-containing iron (II) oxalate or the iron salt of oxalic acid .

Humboldtin crystallizes in the monoclinic crystal system , but rarely develops well-formed, tabular to prismatic crystals with a resin-like sheen on the surfaces. It is mostly found in the form of grape or fibrous to earthy aggregates and crusty coatings of dull yellow to brownish yellow or amber yellow in color. Depending on the form of training, it can be transparent to opaque.

With a Mohs hardness of 1.5 to 2, Humboldtin is one of the soft minerals that, like the reference mineral plaster, can be scratched with the fingernail.

Etymology and history

Alexander von Humboldt (self-portrait from 1814)

Humboldtin was first discovered by August Breithaupt in a weathered lignite deposit near the municipality of Korozluky in Okres Most in the Czech Republic and described in 1821 by Mariano Eduardo de Rivero y Ustariz (1798-1857), who named the mineral after the German naturalist Alexander von Humboldt .

The mineral was already known and characterized when the IMA was founded (1959). Accordingly, Humboldtin is listed as an officially recognized mineral.

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the Humboldtin belonged to the mineral class of "organic compounds" and there to the department of "salts of organic acids", where together with minguzzite , oxammite , stepanovite , weddellite , whewellite and zhemchuzhnikovite it was the " oxalate " -Group "with the system no. IX / A.01 formed.

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. IX / A.01-50 . In the "lapis Classification" this also corresponds to the "organic acid salts" department where Humboldtin together with Antipinit , Caoxit , Coskrenit- (Ce) , Deveroit- (Ce) , Falottait , Glushinskit , Levinsonit- (Y) , Lindbergite , Middlebackit , Minguzzit, moolooite , Natroxalat , Novgorodovait , Oxammit, Stepanovit, weddellite, Wheatleyit , Whewellit, Zhemchuzhnikovit and Zugshunstit- (Ce) , the "group of oxalates [C 2 O 4 ] 2- " form (as 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies the Humboldtin in the “Salts of organic acids” section. This is further subdivided according to the type of salt-forming acid , so that the mineral can be found according to its composition in the sub-section "Oxalates", where it only forms the unnamed group 10.AB.05 together with lindbergite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also assigns the Humboldtin to the class and there in the department of the same name of "organic minerals". Here he is in the " Humboldtin group " named after him with the system no. 50.01.03 and the other members Glushinskit and Lindbergit can be found in the sub-section “Salts of organic acids (oxalates)”.

Crystal structure

Humboldtin crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 12.011  Å ; b  = 5.557 Å; c  = 9.920 Å and β = 128.53 °, as well as four formula units per unit cell . Template: room group / 15

properties

Like all oxalates, Humboldtin also decomposes when heated. First, the water of crystallization is released , and at temperatures above 190 ° C it decomposes with the formation of iron (II) carbonate and carbon monoxide . At even higher temperatures, the iron (II) carbonate changes into iron (II) oxide or the corresponding suboxide .

Compared to other oxalates, the solubility in water can be described as poor. In contrast, Humboldtin is readily soluble in acids . Heated in a test tube ( closed tube , CT) closed with a cotton ball , it releases water and leaves a residue of magnetic iron.

When heated on carbon in front of the soldering tube , Humboldtin first turns black and then red.

Modifications and varieties

So far, no further modifications or varieties of the Humboldtin have been found (as of February 2013). Of synthetic iron (II) oxalate, however, it is known that it can occur in a monoclinic and an orthorhombic crystal form (compare also the properties of iron oxalate ). For this reason, an orthorhombic modification of Humboldtin is conceivable.

Education and Locations

Humboldtin from the Csordakúti mine, Bicske-Csordakút, Fejér County, Hungary (size 13 mm × 13 mm × 4 mm)

Humboldtin is a rare, authentic mineral that occurs predominantly in crevices and crevices in lignite deposits and is usually associated with gypsum and Tschermigite . A purely anthropogenic or biogenic origin as with Moolooit , Glushinskit and Weddellite is theoretically possible and is discussed in the literature. In fact, Humboldtin produced in this way has not yet been detected (as of February 2013).

Even if Humboldtin is the salt of an organic acid, no biological processes or residues of biological activities such as lignite have to be involved in its formation. It can form in granitic pegmatites and hydrothermal mineral deposits , albeit much less frequently . Cassiterite , tourmaline and quartz , among others , can occur here as accompanying minerals .

As a rare mineral formation, Humboldtin has only been found at a few sites so far, with around 20 sites (as of 2013) being known. In addition to its type locality Korozluky , the mineral occurred in the Czech Republic at Čermníky ( Tschermich , flooded by the Nechranice reservoir since 1968 ), Lužice u Mostu ( Luschitz ) and Lomnice u Sokolova ( Lanz ) in Bohemia .

In Germany Humboldtin was previously in Ortenberg in Baden-Württemberg, on the hard Koppe and the Rehberg in the municipality Sailauf in Bavaria in Grossalmerode in Hessen in Potschappel and Altmannsgrün (municipality Tirpersdorf ) in Saxony and in the uranium deposit at Ronneburg (Thuringia) found become.

The only known place of discovery in Austria so far are the Bronze Age slag deposits on Lechnerberg in the municipality of Kaprun (Hohe Tauern, Salzburg).

Other previously known sites include Santa Maria de Itabira in the Brazilian state of Minas Gerais , the tin mine "Wheal Pendarves" near Killivose in the English county of Cornwall , Capoliveri and Porto Azzurro on the Italian island of Elba, Kettle Point in Lambton County and the quarry " Francon ”near Montreal in Canada, the“ Csordakúti Mine ”near Bicske in Hungary as well as Black Mountain in Kern County (California) and the“ Ahmeek Mine ”in Keweenaw County (Michigan) in the USA.

use

Due to the rarity of Humboldtin, there are no practical uses for this mineral. The iron (II) oxalate used in the chemical industry is produced exclusively synthetically.

See also

literature

  • Mariano de Rivero: Note sur une combinaison de l'acide oxalique avec le fer trouvé à Kolowserux, près Belin en Bohéme . In: Annales de chimie et de physique . tape 18 . Paris 1821, p. 207–210 ( rruff.info [PDF; 295 kB ; accessed on December 9, 2019] Humboldtin and Oxalate Iron).

Web links

Commons : Humboldtine  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  798 (first edition: 1891).
  2. ^ David Barthelmy: Humboldtine Mineral Data. In: webmineral.com. Retrieved December 9, 2019 .
  3. ↑ a b c Takuya Echigo, Mitsuyoshi Kimata: Single-crystal X-ray diffraction and spectroscopic studies on humboldtine and lindbergite: weak Jahn – Teller effect of Fe 2+ ion . In: Physics and Chemistry of Minerals . tape 35 , no. 8 , 2008, p. 467-475 , doi : 10.1007 / s00269-008-0241-7 .
  4. ↑ a b c d Humboldtine . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 68  kB ; accessed on December 9, 2019]).
  5. ↑ a b c d e Humboldtine. In: mindat.org. Hudson Institute of Mineralogy, accessed December 9, 2019 .
  6. ^ Jöns Jakob Berzelius : Mineralogy. Humboldtin . In: Annual Report on the Advances in Physical Sciences . tape  2 . Laupp, Tübingen 1823, p. 96 ( limited preview in the Google book search [accessed October 23, 2017] Swedish: Årsberättelse om framstegen i fysik och kemi . Translated by Christian Gottlob Gmelin ).
  7. ↑ Type locality Korozluky (Kolosoruk), Most, Ústí Region, Bohemia (Bohemia), Czech Republic. In: mindat.org. Hudson Institute of Mineralogy, accessed December 9, 2019 .
  8. ↑ Biografia de Mariano Eduardo de Rivero y Ustariz (1798-1857). In: xxvicongresoperuanoquimica2012.wordpress.com. XXVI. Congreso Peruano de Química, September 7, 2012, accessed December 9, 2019 .
  9. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  10. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed December 9, 2019 .
  11. ^ RL Frost, Matt L. Weier: Thermal decomposition of humboldtine - a high resolution thermogravimetric and hot stage Raman spectroscopic study . In: Journal of Thermal Analysis and Calorimetry . tape 75 , no. 1 , 2004, p. 277–291 ( eprints.qut.edu.au [PDF; 439 kB ; accessed on December 9, 2019]).
  12. ^ Edward S. Dana, William E. Ford: Dana's Manual of Mineralogy . 13th edition. John Wiley & Sons, New York 1912, p. 87-88 ( available online at archive.org  - Internet Archive ).
  13. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York et al. 1997, ISBN 0-471-19310-0 , pp. 1011-1012 .
  14. ↑ Orsino Cecil Smith: Identification and Qualitative Chemical Analysis of Minerals . 2nd Edition. Van Nostrand, New York 1953, p. 325 (English).
  15. ^ John White Webster: A Manual of Chemistry . 3. Edition. Marsh, Capen, Lyon and Webb, Boston 1839, pp. 369 ( limited preview in Google Book search).
  16. ↑ Localities for Humboldtine. In: mindat.org. Hudson Institute of Mineralogy, accessed December 9, 2019 .
  17. ↑ List of locations for the Mineralienatlas and Mindat , accessed on December 9, 2019.