Vivianite

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Vivianite
Vivianite-191721 (cropped) .jpg
Blue-green vivianite from the "Morococala Mine", Santa Fé Mining District, Pantaleón Dalence Province , Bolivia ( overall size : 5.9 cm × 3.4 cm × 2.6 cm)
General and classification
other names
  • Anglarite
  • Blue iron earth (after Werner) or blue iron ore
  • Iron blue (after Hausmann)
  • Iron phyllite
  • Glaucosiderite
  • Mullicit
  • Natural Berlin blue
  • Phosphate iron (according to Klaproth)
  • Phosphor iron sinter
  • Iron phosphate
chemical formula Fe 2+ 3 [PO 4 ] 2 • 8H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.CE.40 ( 8th edition : VII / C.10a)
03/40/06/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 10.09  Å ; b  = 13.47 Å; c  = 4.70 Å
β  = 104.3 °
Formula units Z  = 2
Frequent crystal faces tabular according to (010); (310), (100), (001)
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) measured: 2.68 (1); calculated: 2.69
Cleavage completely after {010}
Break ; Tenacity fibrous; flexible, cuttable
colour colorless when fresh; quickly turning blue, green, violet, black-blue
Line color White; becoming bluish or brownish
transparency transparent to translucent
shine Glass gloss, pearlescent
Crystal optics
Refractive indices n α  = 1.579 to 1.616
n β  = 1.602 to 1.656
n γ  = 1.629 to 1.675
Birefringence δ = 0.050 to 0.059
Optical character biaxial positive
Axis angle 2V = 63 ° to 83.5 ° (measured); 78 ° to 88 ° (calculated)
Pleochroism Visible:
X = blue, dark blue to indigo blue
Y = light yellowish green, light bluish green, green yellow
Z = light yellowish green , light yellowish green , olive yellow
Other properties
Chemical behavior oxidizes very quickly in air

Vivianite , also known by various synonyms such as blue iron earth and iron blue , is a frequently occurring mineral from the mineral class of " phosphates , arsenates and vanadates " with the chemical composition Fe 2+ 3 [PO 4 ] 2 · 8H 2 O and thus chemical seen a water-containing iron phosphate (also outdated phosphoric acid iron or phosphoric iron sinter ), more precisely an iron (II) phosphate .

Vivianite crystallizes in the monoclinic crystal system and often develops long, prismatic to needle-like crystals , but also occurs in the form of fibrous to powdery-earthy and radial-ray aggregates . The latter can reach a diameter of around 2 meters, while individual crystals can be up to 1.3 meters long. Visible and undamaged crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer .

Etymology and history

Vivianite was given its name in 1817 by Abraham Gottlob Werner , who named the mineral in honor of the discoverer and first describer John Henry Vivian (1785–1855), a British mineralogist .

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , Vivianite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department "Hydrous phosphates, arsenates and vanadates without foreign anions ", where it gave its name to the "Vivianite series" with the system no. VII / C.10a and the other members Annabergit , Erythrin , Hörnesit , Köttigit and Parasymplesit within the "Bobierrit-Vivianit Group".

In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , 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. VII / C.13-40 . In the "Lapis Classification" This also corresponds to the department "Water-containing phosphates, arsenates and vanadates without foreign anions" where Vivianit with Arupit , Barićit , Bobierrit , Cattiit , Hörnesit, Manganohörnesit , Pakhomovskyit and Parasymplesit forms the "Vivianit group" .

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 vivianite in the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the phosphate, arsenate or vanadate complex (RO 4 ) to the water of crystallization content , so that the mineral can be classified according to its composition in the sub-section “With only medium-sized cations; RO 4  : H 2 O ≤ 1 "is found, where it together with Annabergit, Arupit, Barićit, Erythrin, 2.5 Ferrisymplesit , Hörnesit, Köttigit, Manganohörnesit, Pakhomovskyit and Parasymplesit the" Vivianitgruppe "with the system number. 8.CE.40 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also assigns Vivianite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here, too, he is in the " Vivianite group " with the system no. 40.03.06 within the subsection "Water-containing phosphates etc., with (A 2+ ) 3 (XO 4 ) 2  × x (H 2 O)".

Chemism

Pale blue to almost colorless vivianite crystal from Hagendorf (Waidhaus) , Upper Palatinate, Bavaria (image width 2 mm)

The idealized, theoretical composition of Vivianit Fe 2+ 3 [PO 4 ] 2 · 8H 2 O consists of 33.40% iron (Fe), 12.35% phosphorus (P), 3.22% hydrogen (H) and 51 .03% oxygen (O). In the oxide formula notation, this corresponds to 42.97% FeO , 28.30% P 2 O 5 and 28.73% H 2 O.

In the air, the iron ion in vivianite partially oxidizes from Fe 2+ to Fe 3+ and is transformed into the mineral known as metavivianite with the chemical composition Fe 2+ Fe 3+ 2 (PO 4 ) 2 (OH) 2 · 6H 2 O around. This usually happens very quickly, usually within a few minutes or hours, whereby the process is accelerated by exposure to light.

Crystal structure

Vivianite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 10.09  Å ; b  = 13.47 Å; c  = 4.70 Å and β = 104.3 ° as well as two formula units per unit cell . Template: room group / 12

properties

As a result of the oxidation of the iron, the initially colorless mineral usually turns light to black-blue or green, occasionally also purple or brown. The line color is initially colorless to bluish-white and then turns indigo blue.

Vivianite melts slightly in front of the soldering tube , turns the flame blue-green and becomes magnetic. The mineral is easily soluble in hydrochloric acid (HCl) and nitric acid (HNO 3 ).

Education and Locations

Green Vivianite from the Tomokoni Mine, Potosí, Bolivia (size: 4.6 × 4.5 × 3.1 cm)
Vivianite pseudomorphism after shell from Kerch , Crimea peninsula, Ukraine (size: 5.6 × 4.6 × 2.7 cm)
Dark purple vivianite from the "Blackbird Mine", Lemhi County , Idaho, USA (size: 5.0 × 2.3 × 1.8 cm)

Vivianite is found on magnetic gravel or tin deposits, brown iron stone and in tertiary rock layers . It is also a very common phosphate mineral that is found in clay and peat , although not in large quantities . Under special conditions it can sometimes fill the interior of fossil shells (Kerch), bones and tree trunks.

Vivianite is formed in iron deposits through oxidation ( weathering ), but can also arise there hydrothermally .

Locations include Morococala in Bolivia , Bodenmais , Amberg and Wölfersheim / Wetterau in Germany , Anloua in Cameroon , Kerch in Ukraine and Colorado and Utah in the USA .

Vivianite precipitation (blue) on lawn iron stone

In soils is located Vivianit when ferrous iron and high amounts of phosphate present. Iron (II) is formed from iron (III) under anaerobic conditions as soon as the redox potential of the soil falls below 150 mV. This is especially the case in areas with constantly high water contents; i.e. in backwater , groundwater or bog soils . In most natural soils, however, the phosphate content required for significant vivianite formation is not sufficient. Under the original conditions, almost only fens achieve this level . These low-lying biotopes are often nutrient sinks and contain a lot of organic material that releases phosphate during biodegradation. The mineralization is reinforced by drainage , so that Vivianite is widespread in drained bog areas.

Since phosphorus is an important plant nutrient , in modern agriculture is fertilized regularly and extensively with phosphates . As a result, many soils today contain enough phosphate for the formation of vivianite.

If iron (II) and phosphate come together in the soil, the chemical compound there is initially colorless due to the lack of oxygen. The typical blue color appears only when air is supplied. As a result of evaporation, dissolved Vivianite can be transported with the water to the surface and precipitate there . Over time, clearly visible deposits form. Vivianite is the only natural explanation for an intense blue soil color in Germany.

An interesting formation was observed in 1984 at a site in the Harz (upper Selketal). During renovation work on the small railway line between the Stiege (Harz) and Albrechtshaus stations , the railway workers came across racing fire slag and bone fragments from cattle and horses at a depth of 1.3 m. The bone parts were completely discolored light blue. Six nearby horse teeth looked the same. In this layer of earth was ceramics that allowed dating to the 10th to 12th centuries . The medullary cavities of the extremity bones and the pulp cavities of the teeth were filled with elongated, fused, dark blue crystals up to 3 mm in length.

The following conditions led to the formation of crystals: carbonate apatite of the bones, hydroxyapatite of the dentine and fluorapatite of the tooth enamel in contact with an aqueous solution containing bivalent iron. The calcium was exchanged for iron over a longer period of time , since Vivianite is less soluble. The fluorine-containing, more resistant tooth enamel did not change. Under the conditions of delayed ion exchange - cavernous spaces in the tooth and bone interior - particularly large and uniform crystals were created. The ceramic finds provide evidence of a period for crystal formation. Vivianite sites in the Harz Mountains:

Further bone finds with vivianite formation:

  • 1933 - in a horse's skull (from an old mine in Příbram , Czech Republic).
  • 1962 - Horse skull (from the moorland of Feistritz-Pulst, Glantal , Austria).

The assumption (cf. Muus and Dahlstrøm: Meeresfische; 1978) that the green pigment in the bones of the north- east Atlantic eel mother ( Zoarces viviparus ) and common garfish ( Belone belone ) consists of vivianite ("green bones") has been refuted by recent research. The iron phosphate content is not high enough. Biliverdin is responsible for the green color .

use

As a pigment

Vivianite is an ancient blue dye that has probably been used since ancient times and played a role in panel painting in the High Middle Ages .

As a pigment it is known as iron blue , but it is not very stable. Today it only plays a role in dealing with historical paintings, for example in restoration . The use of the name Eisenblau, however, leads to confusion with Berlin Blue , since "Eisenblau" is its synonym in the industry .

As a gem

Vivianite is unsuitable for commercial use as a gemstone due to its minimal hardness and its perfect cleavability. However, it is a sought-after object for exchange or sale among collectors and hobbyists.

See also

literature

Monographs
  • Mark Richter: The use of Vivianite in the colored version and painting of the Baroque and Rococo . In: Michael Kühlenthal (Hrsg.): Historische Polychromie . Hirmer, Munich 2004, ISBN 3-7774-9900-5 , p. 204-212 .
  • Hartmut Knappe, Jürgen Siemroth: Minerals from the Harz - Vivianite . In: The Harz - a landscape introduces itself . tape 13/14 . Harz Museum, Wernigerode 1985, p. 42 .
In compendia
  • Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 176 .

Web links

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

Individual evidence

  1. ↑ a b c d Vivianite . In: Meyers Konversations-Lexikon . 4th edition. Volume 16, Verlag des Bibliographisches Institut, Leipzig / Vienna 1885–1892, p. 236.
  2. ↑ a b c d e Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 340-341 .
  3. ^ Phosphorus . In: Meyers Konversations-Lexikon . 4th edition. Volume 13, Verlag des Bibliographisches Institut, Leipzig / Vienna 1885–1892, p. 8.
  4. ↑ 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.  481 .
  5. ↑ a b c d e Vivianite . 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; 66  kB ; accessed on July 27, 2019]).
  6. ↑ a b c d e f Vivianite. In: mindat.org. Hudson Institute of Mineralogy, accessed July 27, 2019 .
  7. ↑ Vivianite - Vivianite - Vivianite - Vivianita. In: giantcrystals.strahl.org. The Giant Crystal Project Site, archived from the original on January 21, 2017 ; accessed on July 27, 2019 (English).
  8. ↑ 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 .
  9. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 25, 2019 .
  10. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: May 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2019, accessed May 20, 2019 .
  11. ↑ a b Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 .
  12. ↑ Comparative image of Vivianite in the fresh, colorless state and converted into light blue metavivianite two hours later after exposure to air and light. In: mindat.org. Hudson Institute of Mineralogy, accessed July 27, 2019 .
  13. ↑ Comparison picture of Vivianite in the fresh, colorless state and four days later converted into light blue Metavivianite by exposure to air. In: mindat.org. Hudson Institute of Mineralogy, accessed July 27, 2019 .
  14. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  642–643 (first edition: 1891).
  15. ↑ G. Grosse-Brauckmann: Deposits of the moors . In: Karlhans Göttlich (ed.): Moor and peat science . E. Schweizerbart´sche Verlagbuchhandlung, Stuttgart 1990, ISBN 3-510-65139-1 , p. 229 .
  16. ↑ Frank Jüttner, Maike Stiesch, Waldemar Ternes: Biliverdin: the blue-green pigment in the bones of the garfish (Belone belone) and eelpout (Zoarces viviparus) . In: European Food Research and Technology . March 2013, doi : 10.1007 / s00217-013-1932-y (English, []).
  17. ↑ Volkert Emrath: Some old pigments and dyes, their origin u. Period of use in panel, book and miniature painting before approx. 1780. May 9, 2006.
  18. ↑ 10400: Vivianite natural, iron blue, blue iron ore. In: kremer-pigmente.de. Kremer Pigments, archived from the original on March 13, 2016 ; accessed on July 27, 2019 .
  19. ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 224 .