Akatoreit

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Akatoreit
Akatoreite-detail.jpg
Yellowish to brownish-yellow deposits of akatorite in a matrix of pink rhodonite.
Location of the mineral sample : Akatore Creek near Dunedin , New Zealand's South Island
General and classification
other names

IMA 1969-015

chemical formula
  • Mn 2+ 9 Al 2 Si 8 O 24 (OH) 8
  • Mn 2+ 9 Al 2 [(OH) 3 | (Si 4 O 12 ) (OH)] 2
  • (Mn 2+ , Fe 2+ ) 9 Al 2 [(OH) 3 | Si 4 O 12 (OH)] 2
Mineral class
(and possibly department) 		Silicates and germanates - group silicates (sorosilicates)
System no. to Strunz
and to Dana 		9.BH.15 ( 8th edition : VIII / C.35)
57.02.03.01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Space group P 1 (No. 2)Template: room group / 2
Lattice parameters a  = 8.34  Å ; b  = 10.37 Å; c  = 7.63 Å,
α  = 104.5 °; β  = 93.8 °; γ  = 104.2 °
Formula units Z  = 1
Frequent crystal faces (010), (0 1 1), (0 4 3), (0 2 1), (0 3 1), ( 11 1), (1 3 3)
Twinning after {0 2 1}
Physical Properties
Mohs hardness 6th
Density (g / cm 3 ) measured: 3.48; calculated: 3.47
Cleavage good after {010}, indistinct after {0 1 2}
colour yellow-orange to orange-brown
Line color yellowish white
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.698
n β  = 1.704
n γ  = 1.720
Birefringence δ = 0.022
Optical character biaxial positive
Axis angle 2V = 65 ° (measured), 64 ° (calculated)
Pleochroism X = colorless; Y = light yellow; Z = pale canary yellow

Akatoreit is a very rarely occurring mineral from the mineral class of "silicates and germanates" with the chemical composition Mn 2+ 9 Al 2 [(OH) 3 | (Si 4 O 12 ) (OH)] 2 and thus chemically a manganese - aluminum - silicate with additional hydroxide . Structurally, Akatoreite belongs to the group silicates (sorosilicates).

Akatoreit crystallizes in the triclinic crystal system , but only rarely develops prismatic and parallel to the a-axis [100] striped crystals or sheaf-shaped to radial-rayed crystal aggregates up to about one centimeter in size that are visible to the naked eye . It is mostly found in the form of fibrous, fine-grained or coarse masses. The transparent crystals are yellow-orange to orange-brown in color with a glass-like sheen on the surfaces. Akatoreit leaves a yellowish-white line on the marking board .

Etymology and history

Akatoreite was first discovered in mineral samples from a manganese - containing ore lens about 3 km south of Akatore Creek in the Clutha District on the South Island of New Zealand. The manganese lens was described in 1958 by P. Robinson. Upon subsequent examination of the opaque minerals in this deposit, HH Khoo also noticed a previously unknown, fibrous and yellow mineral.

Peter B. Read and Anthony Reay succeeded in obtaining the quantities of type material necessary for an analysis of the mineral . They were able to confirm the discovery of a previously unknown new type of mineral and named the mineral after its type locality . After the International Mineralogical Association (internal entry number of the IMA: 1969-015 ) examined and recognized the Akatoreite as a new mineral species , the first description of the mineral was published in 1971 in the scientific journal American Mineralogist .

The type material of the mineral is recorded at the University of Otago in Dunedin (catalog number unknown) and the Geological Survey of New Zealand in Lower Hutt (catalog number P39193 ) in New Zealand and the National Museum of Natural History in Washington, DC in the USA (catalog nos. 137285 and 142541 ).

classification

Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , Akatoreit belonged to the mineral class of "silicates and germanates" and there to the department of " group silicates (sorosilicates)", where together with Hubeit and Ruizit it formed the unnamed group VIII /C.35 formed.

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 assigns Akatoreit to the group of "group silicates". However, this is further subdivided according to the structure of the silicate groups and the coordination of the cations involved , so that the mineral is classified in the sub-section “Group silicates with Si 3 O 10 or larger anions ; Cations in tetrahedral [4] and greater coordination ”can be found, where it is the only member of the unnamed group 9.BH.15 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Akatoreit to the class of "Silicates and Germanates" and there into the department of "Group silicates: insulars (Si 3 O 10 ) and larger non-cyclic groups with Si 3 O 10 - Groups ". Here he is together with Cassagnait and Hubeit in the " Akatoreitgruppe " with the system no. 57.02.03 within the sub-section "Group Silicates : Insular (Si 3 O 10 ) and larger non-cyclic groups with Si 4 O 13 groups".

Chemism

The idealized, theoretical compound Mn 2+ 9 Al 2 [(OH) 3 | (Si 4 O 12 ) (OH)] 2 consists of 38.24% manganese (Mn), 4.17% aluminum (Al), 17, 38% silicon (Si), 39.59% oxygen (O) and 0.62% hydrogen (all data in% by weight).

However, the microprobe analysis on the type material showed, in addition to 47.7% Mn, 36.4% SiO 2 , 8.3% Al 2 O 3 and 6.21% H 2 O, in addition small foreign admixtures of 1.0% iron, 0, 3% MgO and 0.2% CaO and traces of TiO 2 (0.03%). The empirical formula is calculated according to (Mn 8.61 Fe 0.19 Mg 0.09 Ca 0.05 ) Σ = 8.94 Si 7.75 Al 2.09 O 23.17 (OH) 8.83 .

Crystal structure

Crystal structure of Akatoreite

Akatoreit crystallizes monoclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 8.34  Å ; b  = 10.37 Å; c  = 7.63 Å; α = 104.5 °; β = 93.8 ° and γ = 104.2 ° and one formula unit per unit cell . Template: room group / 2

Education and Locations

Akatoreit formed in weakly metamorphosed , manganese-containing chert - and carbonate - lenses in slate , but can also manganese and potassium-rich , felsic meta volcanics occur. Depending on the locality can Alabandin , apatite , Ganophyllit , Hübnerit , Pyrolusit , Pyroxmangit , quartz , rhodochrosite , rhodonite , Spessartin , Tinzenite , Todorokit as accompanying minerals occur.

Akatoreite is one of the very rare mineral formations that were only known in a few samples. In addition to its first discovery in Akatore Creek , which is the only known site in New Zealand so far, the mineral has so far (as of 2018) only been found in a manganese deposit at about 3000 meters above sea level on Monte Maniglia in the Italian municipality of Bellino (Piedmont) and in the Häste iron and manganese ore field in the Swedish municipality of Norberg (Västmanland).

A new find, initially referred to as Akatoreit, in the iron-manganese deposit Kamoyama Mine near Ino in the prefecture of Kōchi on the Japanese island of Shikoku subsequently turned out to be the mineral bunnoite , which was discovered and recognized in 2014 .

See also

literature

  • Peter B. Read, Anthony Reay: Akatoreite, a new manganese silicate from eastern Otago, New Zealand . In: American Mineralogist . tape 56 , 1971, p. 416–426 (English, rruff.info [PDF; 645 kB ; accessed on September 22, 2018]).
  • P. Ounchanum, S. Morad: Paragenesis of akatoreite and ganophyllite in the manganiferous rocks of the Häste Field, Norberg ore district, central Sweden . In: New Yearbook for Mineralogy, Treatises . tape 157 , 1987, pp. 225-244 (English).
  • Peter C. Burns, Frank C. Hawthorne: Edge-sharing Mn 2+ O 4 tetrahedra in the structure of akatoreite, Mn 2+ 9 Al 2 Si 8 O 24 (OH) 8 . In: The Canadian Mineralogist . tape 31 , 1993, pp. 321–329 (English, rruff.info [PDF; 841 kB ; accessed on September 22, 2018]).
  • John L. Jambor, Edward S. Grew: New mineral names . In: American Mineralogist . tape 79 , 1994, pp. 185–189 (English, rruff.info [PDF; 490 kB ; accessed on September 22, 2018]).
  • 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 .

Web links

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

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: July 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, July 2019, accessed May 20, 2019 .
  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.  590 (English).
  3. ↑ a b 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 .
  4. ↑ David Barthelmy: Akatoreite Mineral Data. In: webmineral.com. Retrieved on August 22, 2019 .
  5. ^ A b c Peter B. Read, Anthony Reay: Akatoreite, a new manganese silicate from eastern Otago, New Zealand . In: American Mineralogist . tape 56 , 1971, p. 416–426 (English, rruff.info [PDF; 645 kB ; accessed on September 22, 2018]).
  6. ↑ a b c d e f g Akatoreite . 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; 74  kB ; accessed on September 22, 2018]).
  7. ↑ a b c d e Akatoreite. In: mindat.org. Hudson Institute of Mineralogy, accessed August 22, 2019 .
  8. ↑ Catalog of Type Mineral Specimens - A. (PDF 82 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed on August 22, 2019 (Akatoreit p. 3).
  9. ↑ Mineralienatlas: Akatoreit
  10. ↑ Find location list for Akatoreit in the Mineralienatlas and in Mindat
  11. ↑ Akatoreite from Kamoyama mine, Ino, Kochi Prefecture, Shikoku Island, Japan. In: mindat.org. Hudson Institute of Mineralogy, accessed August 22, 2019 .