Allanite

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Allanite
Allanite-609403.jpg
Allanite from the Tripp Mine, Cardiff Township, Haliburton County , Ontario, Canada (size 46 mm × 24 mm × 10 mm)
General and classification
other names

Orthite

chemical formula (CaSEE) (Al 2 Fe II ) (Si 3 O 11 ) O (OH)
Mineral class
(and possibly department) 		Silicates and germanates - group silicates (sorosilicates)
System no. to Strunz
and to Dana 		9.BG.05b ( 8th edition : VIII / C.23)
58.02.01c.01 to 58.02.01c.03
Similar minerals Oxyallanite, ferriallanite, dissakisite , dollaseite, epidote , clinozoisite
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) P 2 1 / m (No. 11)
Lattice parameters see crystal structure
Formula units Z  = 2
Frequent crystal faces (100), (001), (101), (110), (20 1 )
Twinning rarely after {100}
Physical Properties
Mohs hardness 5.5 to 6.5
Density (g / cm 3 ) 3.4 to 4.2
Cleavage indistinct after {001}, {100}, {110}
Break ; Tenacity shell-like to uneven; brittle
colour black, light to dark brown, often with a rusty coating
Line color brownish to greenish
transparency opaque
shine Greasy to glass gloss
radioactivity radioactive
Crystal optics
Refractive indices n α  = 1.690 to 1.813
n β  = 1.700 to 1.857
n γ  = 1.706 to 1.891
Birefringence δ = 0.013 to 0.036
Optical character biaxial + or -
Axis angle 2V = 40 to 90 ° (-); 90 to 57 ° (+)
Pleochroism different shades of brown
Other properties
Special features often radial cracks around allanite

Allanite (also orthite ) is the collective name for an unspecified mineral of a mixed crystal series with the end members allanite (Ce) , allanite (La) , allanite (Nd) and allanite (Y ) recognized by the International Mineralogical Association (IMA) ) from the mineral class of "silicates and germanates". Structurally, the allanites belong to the group silicates (sorosilicates).

All members of the Allanit series crystallize in the monoclinic crystal system with the following idealized chemical composition :

  • Allanite- (Ce) - CaCe (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ]
  • Allanite- (La) - CaLa (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ]
  • Allanite- (Nd) - CaNd (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ]
  • Allanite- (Y) - CaY (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ]

Due to the mixed crystal formation, the metals cerium (Ce), lanthanum (La), neodymium (Nd) and yttrium (Y), known as rare earths, can represent each other in the formula ( substitution , diadochia), but are always in the same proportion to the other constituents of the mineral. The mixed crystal formula is therefore partly given as Ca SEE (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ] (English Ca REE ...). Even if this notation is often used, the exact notation (Ca, La, Nd, Y) (Al 2 Fe 2+ ) [O | OH | SiO 4 | Si 2 O 7 ] should be preferred, otherwise it will be confused with the chemical symbol S for sulfur is possible.

Allanite usually develops thick tabular crystals , but also occurs in the form of granular to massive mineral aggregates of gray, brown or black color.

Etymology and history

The mineral was first discovered by Carl Ludwig Giesecke (1761–1833) in Greenland. He sent his mineral samples to Copenhagen for analysis , but the ship was hijacked by the English and all cargo was sold in Scotland . The mineral samples were acquired by the Scottish mineralogist Thomas Allan (1777–1833), who recognized the Greenlandic origin from the cryolite samples that were also contained . Allan sent some of the samples to Thomas Thomson for analysis , who named the newly discovered mineral allanite.
The term orthite chosen by Jöns Jakob Berzelius in 1818 due to the mostly right-angled, elongated shapes of the crystals did not prevail and is now considered a synonym for allanite.

The type locality for the individual minerals applies to

There is no type locality for allanite- (Y), as this end member of the allanite mixed series was renamed in the course of the reorganization of the nomenclature of rare earth minerals by Alfred Abraham Levinson in 1966 , but has not yet been described independently.

Allanite- (Ce) type material is stored in the University of Copenhagen in Denmark (Catalog No. 5, 6) and the Natural History Museum in London, England (Catalog No. 94377).

classification

Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the allanites belonged to the mineral class of "silicates and germanates" and there to the department of "group silicates (sorosilicates)", where they together with dissakisite (Ce) , dissakisite - (La) , Dollaseit- (Ce) , epidote , epidote (Pb) , Ferriallanit- (Ce) , Gatelit- (Ce) , clinozoisite , Klinozoisit- (Sr) , Khristovit- (Ce) , Manganiandrosit- (Ce) , Manganiandrosit- (La) , Tweddillit , Mukhinit , Piemontit , Piemontit- (Sr) , Uedait- (Ce) , Vanadoandrosit- (Ce) , Västmanlandit- (Ce) and Zoisit the " Epidotgruppe " with the system number. VIII / C.23 .

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 the allanites in the category of "group silicates (sorosilicates)". This is, however, further subdivided according to the structure of the silicate groups and the coordination of the cations involved , so that the minerals according to their structure in the subdivision of “group silicates with mixed SiO 4 and Si 2 O 7 groups; Cations in octahedral [6] and greater coordination "are to be found, where they are found together with androsite (La), chromallanite (REE), chromoandrosite (REE), chromodissakisite (REE), dissakisite (Ce), Dissakisite- (La), Ferriallanite- (Ce), Ferriandrosite- (REE), Ferridissakisite- (REE), Manganiandrosite- (Ce), Manganiandrosite- (La) (Rn), Manganidissakisite- (REE), Uedaite- (Ce) , Vanadoallanit- (REE), Vanadoandrosit- (Ce) and Vanadodissakisit- (REE) the newly defined, unnamed group with the system no. 9.BG.05b form.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the allanites to the class of “silicates and Germanates”, but there in the more finely subdivided division of “group silicates: insular, mixed, individual and larger tetrahedral groups”. Here they are together with epidote, epidote (Pb), epidote (Sr), gatelite (Ce), clinozoisite, clinozoisite (Sr), tweddillite, mukhinite, piemontite, piemontite (Sr) and uedaite (Ce) in the " epidote group (allanite subgroup) " with the system no. 58.02.01c within the sub-section “Group Silicates : Insular, mixed, single and larger tetrahedral groups with cations in [6] and higher coordination; Single and double groups (n = 1,2) ”.

Crystal structure

All allanites crystallize in the monoclinic crystal system in the space group P 2 1 / m (space group no.11) with the following lattice parameters with two formula units per unit cell :

  • Allanite- (Ce) - a  = 8.93  Å ; b  = 5.76 Å; c  = 10.15 Å and β = 114.8 °
  • Allanite- (La) - a  = 8.94 Å; b  = 5.726 Å; c  = 10.16 Å and β = 114.7 °
  • Allanite- (Nd) - a  = 8.8897; b  = 5.7308; c  = 10.1010 and β = 115.166
  • Allanite- (Y) - a  = 8.98 Å; b  = 5.75 Å; c  = 10.23 Å ​​and β = 115 °

properties

Through substitution one can find numerous other elements in allanite such as thorium , manganese , titanium , magnesium and trivalent iron .

Due to the chemical similarity of uranium and thorium to rare earths, the mineral can incorporate significant quantities of these radioactive substances into the grid and thus be radioactive. Assuming a proportion of 5% uranium / thorium with respect to the REE is a mineral for the specific activity of between 0.112 k Bq / g and / kBq indicated 0.613 g (compared to natural potassium 0.0312 kBq / g). The series of decays produce a multiple of the activity of uranium or thorium. The quoted value can vary significantly depending on the mineral content and composition of the levels. Selective enrichment or depletion of the radioactive decay products are also possible and change the activity.

Due to its natural radioactivity, allanite crystals are mostly metamictic ( isotropic ), i.e. the crystal structure was partially or completely destroyed by the ionizing radiation. As a result, the mineral loses its directional, physical properties (hardness, refractive index) over time and becomes opaque black.

Modifications and varieties

There are a number of minerals related to allanite. Dissakisite and Dollaseit are Mg variants, ferricallanite contains Fe 2+ as well as Fe 3+ , oxyallanite Fe 3+ and no OH group.

Education and Locations

Allanite (black) and Törnebohmit- (Ce) ( small gray veins in the allanite) from Jamestown in Boulder County , Colorado (size: 6.5 cm × 3.8 cm × 2.5 cm)
Allanite on quartz from White Mountain, Lincoln County (New Mexico) , USA (size: 2.7 cm × 1.8 cm × 1.7 cm)

Allanite is a common accessory component in many igneous rocks , especially in granites , granodiorites , diorites and syenites and their pegmatites . Allanite can also be found in metamorphic rocks, the parent rocks of which contain rare earths, from the epizone (100–300 ° C, low pressure) to the katazone (over 700 ° C, high pressure). In addition, allanite occurs as a hydrothermal formation. As accompanying minerals may vary by locality, among others, epidote, Euxenite , fluorite , Gadolinit , monazite and muscovite occur.

As a frequent mineral formation, allanites are generally to be found at many sites, with a total of around 1,800 sites known to date (as of 2014). However, since these finds are rarely analyzed with sufficient precision, information on the individual English members with regard to the number of sites is accordingly inaccurate. Merely due to the fact that cerium is one of the most frequently occurring rare earth metals, the number of known sites for the end link allanite- (Ce) with a little more than 600 is accordingly far higher than that of the other end links (allanite- (La) and - (Y) about 20 localities; allanite- (Nd) about 4 localities).

Bancroft in the Canadian province of Ontario is known for its extraordinary allanite finds , where granular aggregates of up to 70 centimeters in diameter were discovered.

In Germany, the mineral is known from various places in the Black Forest ; from several places in the Franconian Forest , the Spessart , the Bavarian Forest and the Upper Palatinate in Bavaria; from many places in the Hessian Odenwald ; from the Okertal and the Radautal in Lower Saxony; from some places around the Laacher See in the Rhineland-Palatinate Vulkaneifel ; from Petersberg in Saxony-Anhalt; from some places in the Ore Mountains and Upper Lusatia in Saxony as well as from Neumühle / Elster (Greiz) and Weitisberga in Thuringia.

In Austria, Allanite has so far been found on the Ankogel group , the Koralpe and some other areas in Carinthia ; in several places in the Lower Austrian Waldviertel ; in the Nassfeldtal , in the Hüttwinkltal and other areas in the Hohe Tauern in Salzburg; around Freistadt and in the district Rohrbach in Upper Austria as well as in a magnetite - prospecting at Kleinwöllmiß (municipality Sankt Martin am Wöllmißberg ), in pockets in the municipality Peggau and rock samples in the construction of forest tunnel in the Pyhrn motorway near the village Forest on the Schober Pass in Styria.

In Switzerland the mineral could be found on the Grimsel Pass in the canton of Bern; can be found in various valleys in the canton of Graubünden , in many places in the Val d'Anniviers and in the Binn valley and at some sites in the cantons of Ticino and Uri .

Other sites are in Afghanistan, Egypt, Algeria, the Antarctic, Argentina, Armenia, Australia, Bolivia, Brazil, Bulgaria, China, Finland, France, Greece, Greenland, Guyana, India, Indonesia, Iran, Ireland, Italy, Japan , Cameroon, Kazakhstan, Kenya, Korea, Madagascar, Morocco, Mexico, Mongolia, Mozambique, Namibia, New Zealand, Norway, Pakistan, Poland, Portugal, Romania, Russia, Sweden, Slovakia, Somalia, Somaliland, Spain, South Africa, Swaziland , Taiwan, Tajikistan, Tanzania, Thailand, the Czech Republic, Turkey, Ukraine, Hungary, Uzbekistan, the United Arab Emirates, the United Kingdom (England, Scotland, Wales) and the United States of America, Vietnam.

use

Allanite is a primary source of the rare earth group metals.

See also

literature

  • Thomas Thomson: Experiments on allanite, a new mineral from Greenland. In: A Journal of Natural Philosophy, Chemistry, and the Arts. Volume 29, 1811, pp. 47-59. ( PDF 526.5 kB )
  • Thomas Thomson: Experiments on allanite, a new mineral from Greenland. In: Transactions of the Royal Society of Edinburgh. Volume 6, 1812, pp. 371-386. ( PDF 2.45 MB )
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 698 (first edition: 1891).
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin / New York 1981, ISBN 3-11-006823-0 , p. 723-724 .
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th, revised and expanded edition. German publishing house for basic industry, Leipzig 1987, ISBN 3-342-00288-3 , p. 506 .

Web links

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

Individual evidence

  1. ↑ a b Mindat - Allanite- (Y)
  2. ^ A b c 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.  586 .
  3. ^ IMA / CNMNC List of Mineral Names; March 2014 (PDF 1.53 MB)
  4. ↑ a b 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. 168, 287 .
  5. ^ AA Levinson: A system of nomenclature for rare-earth minerals. In: American Mineralogist. Volume 51, 1966, pp. 152–158 ( PDF 282.8 kB )
  6. ^ Allanite- (Ce). In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF 72.6 kB )
  7. ↑ American-Mineralogist-Crystal-Structure-Database - Allanite
  8. ↑ Webmineral - Allanite- (Y)
  9. ↑ R. Gieré, SS Sorensen: Allanite and other REE-rich epidote-group minerals. In: A. Liebscher, G. Franz (Ed.): Epidotes. In: Reviews in Mineralogy & Geochemistry. Volume 56, 2004, pp. 431-493.
  10. ↑ Webmineral: Radioactivity in Minerals - The calculation of radioactivity in minerals
  11. ↑ Webmineral - Allanite- (La)
  12. ↑ Webmineral - Allanite- (Ce)
  13. ↑ Mindat - Number of localities for Allanite
  14. ↑ Mindat - Number of localities for Allanite- (Ce)
  15. ↑ Mindat - number of localities for Allanite- (La) , Allanite- (Y) and Allanite- (Nd)
  16. ^ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 215 (allanite- (Ce)) .
  17. ↑ Find location list for Allanite in the Mineralienatlas and Mindat