Ernstit

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Ernstit
Ernstite-179857.jpg
Pseudomorphosis from Ernstit to Childrenit from Boa Esperança, Linópolis , Divino das Laranjeiras , Minas Gerais , Brazil (size: 4 × 2.8 × 2.7 cm)
General and classification
other names

IMA 1970-012

chemical formula
  • (Mn 2+ , Fe 3+ ) Al (PO 4 ) (OH, O) 2
  • (Mn 2+ , Fe 3+ ) Al [(OH, O) 2 | PO 4 ]
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DD.20
42.07.01.03
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic; m or
monoclinic prismatic; 2 / m
Space group Aa (No. 9, position 4) or A 2 / a (No. 15, position 4)Template: room group / 9.4
Template: room group / 15.4
Lattice parameters a  = 13.32  Å ; b  = 10.50 Å; c  = 6.97 Å
β  = 90.4 °
Formula units Z  = 8
Frequent crystal faces {110}, {211}, { 2 11}, rarely also {100} and {010}
Physical Properties
Mohs hardness 3 to 3.5
Density (g / cm 3 ) measured: 2.07; calculated: 3.086
Cleavage very good after {100}, good after {010}
Break ; Tenacity not defined
colour yellowish brown
Line color not defined
transparency translucent
shine not defined
Crystal optics
Refractive indices n α  = 1.678
n β  = 1.706
n γ  = 1.721
Birefringence δ = 0.043
Optical character biaxial negative
Axis angle 2V = 74 ° (measured); 70 ° (calculated)
Pleochroism visible:
X = yellowish brown
Y = red brown
Z = light yellow

Ernstit is a very seldom occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition (Mn 2+ , Fe 3+ ) Al [(OH, O) 2 | PO 4 ] and thus chemically a manganese - Iron - aluminum - phosphate with additional oxygen or hydroxide ions . The elements manganese and iron indicated in the round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral.

Ernstit crystallizes in the monoclinic crystal system and develops small, prismatic crystals up to about 15 millimeters in size with a yellowish-brown color, which are arranged in radial mineral aggregates . Pseudomorphoses from Ernstit to Childrenit are also known .

Etymology and history

Ernstit was first discovered near the Davib-Ost farm in the municipality of Karibib (Erongo region) in Namibia and described in 1970 by Erich Seeliger and Arno Mücke (* 1937), who named the mineral after the German mineralogist Theodor Ernst .

The type material (holotype) of the mineral is stored in the Institute for Mineralogy and Crystallography at the Technical University of Berlin under the collection no. 92/53 (crystal aggregate about 13 mm long as a crusty coating on apatite ). Another piece is in the National Museum of Natural History in Washington, DC in the USA under catalog no. 145620 deposited.

classification

The Ernstit is not yet listed in the outdated 8th edition of the Strunz mineral classification . Only in the Lapis mineral directory , which was revised and updated in 2018 by Stefan Weiß, which is still based on this classic system from Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system and mineral number. VII / D.14-30 . In the "lapis system" this corresponds to the class of "phosphates, arsenates and vanadates" and there the department "water-containing phosphates, with foreign anions ", where Ernstit forms an independent but unnamed group together with childrenite and eosphorite .

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 assigns the Ernstit to the department of “Phosphates etc. with additional anions; with H 2 O “. However, this is more precisely subdivided according to the relative size of the cations involved and the ratio between the other anions (OH, etc.) and the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral is classified in the sub-section " With only medium-sized cations; (OH etc.): RO 4  = 2: 1 "can be found, where the" Childrenite group "with the system no. Is also found together with Childrenite and Eosphorite. 8.DD.20 forms.

The systematics of minerals according to Dana also assigns the Ernstit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc., with hydroxyl or halogen". Here he is together with Childrenit, Eosphorit and Sinkankasit in the "Childrenite group" with the system no. 42.07.01 to be found in the sub-section of " Water-containing phosphates etc., with hydroxyl or halogen and the general composition (AB) 5 (XO 4 ) 3 Z q  • x (H 2 O) ".

Crystal structure

Ernstit crystallizes monoclinically in space group Aa (space group no. 9, position 4) or A 2 / a (no. 15, position 4) with the lattice parameters a  = 13.32  Å ; b  = 10.50 Å; c  = 6.97 Å and β = 90.4 ° and 8 formula units per unit cell . Template: room group / 9.4Template: room group / 15.4

Education and Locations

Ernstit formed by oxidation of Eosphorit and is therefore often associated with this in granite - pegmatites .

As a rare mineral formation, Ernstit could only be proven at a few sites, whereby so far (status: 2013) around 10 sites are known. In addition to its type locality Farm Davib-Ost in Namibia, these include the “St. John's ”near Kapunda in Australia, the“ Boa Esperança ” prospect near Linópolis in the Brazilian municipality of Divino das Laranjeiras ( Minas Gerais ), the Big Fish River near Dawson in the Yukon territory in Canada, Eräjärvi / Orivesi in Finland and the“ White Cap “Near Keystone in the US state of South Dakota .

See also

literature

  • E. Seeliger, A. Mücke: Ernstit, a new Mn 2+ - Fe 3+ - Al - phosphate and its relationship to eosphorite . In: New Yearbook of Mineralogy, monthly books . 1970, p. 289-298 .
  • Michael Fleischer : New Mineral Names . In: American Mineralogist . tape 56 , 1971, p. 631–640 (English, rruff.info [PDF; 737 kB ; accessed on September 3, 2019]).
  • GMD Costa, R. Scholz, J. Karfunkel, V. Bermanec, MLDSC Chaves: Fe-Mössbauer spectroscopy on natural phosphorite-childrenite-ernstite samples . In: Physics and Chemistry of Minerals . tape 31 , 2005, p. 714–720 , doi : 10.1007 / s00269-004-0434-7 (English, researchgate.net [PDF; 608 kB ; accessed on September 3, 2019]).
  • 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 , p. 634 .

Web links

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

Individual evidence

  1. ↑ 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 September 3, 2019 .
  2. ↑ 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.  504 (English).
  3. ↑ a b c d Ernstite . 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; 65  kB ; accessed on September 3, 2019]).
  4. ↑ a b c d e f Ernstite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 3, 2019 .
  5. ↑ Seeligerite . 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; 63  kB ; accessed on September 3, 2019]).
  6. ↑ Mückeite . 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; 61  kB ; accessed on September 3, 2019]).
  7. ↑ Catalog of Type Mineral Specimens - E. (PDF 40 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed September 3, 2019 .
  8. ^ Type mineral catalog Germany - Ernstit. In: typmineral.uni-hamburg.de. University of Hamburg , December 8, 2017, accessed on September 3, 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 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 3, 2019 .
  11. ↑ Localities for Ernstite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 3, 2019 .
  12. ↑ Find location list for Ernstit in the Mineralienatlas and in Mindat