Freboldit

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Freboldit
General and classification
chemical formula
  • CoSe
  • γ-CoSe
Mineral class
(and possibly department) 		Sulfides and sulfosalts (including selenides, tellurides, arsenides, antimonides, bismuthides, sulfarsenites, sulfantimonites, sulfbismuthites)
System no. to Strunz
and to Dana 		02.CC.05 ( 8th edition : II / B.09a)
02.08.11.10
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 3 / mmc (No. 194)Template: room group / 194
Lattice parameters a  = 3.63  Å ; c  = 5.30 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) calculated: 7.70
Cleavage is missing
colour copper red, gray black
Line color not defined
transparency opaque (opaque)
shine Metallic luster

Freboldit is a very rare occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical composition COSE and chemical terms, a cobalt selenide . As close relatives of the sulfides, the selenides are placed in the same class.

Freboldite crystallizes in the hexagonal crystal system and is mainly found in the form of coarse mineral aggregates or embedded grains from copper-red to gray-black in color. The mineral is in any form opaque ( opaque ) and displays on the surfaces of a metallic luster .

Etymology and history

The mineral was first discovered together with Bornhardtit , Trogtalit , Hastit (discredited 2009, identical to Ferroselite ) in the Trogtal quarry near Lautenthal in the Lower Saxony district of Goslar . It was first described in 1955 by Paul Ramdohr and Margaret Schmitt , although initially without giving the mineral a name, as the results of the X-ray powder diagram were unsatisfactory due to the small amount of sample. Hugo Strunz was only able to identify the mineral as cobalt selenide (CoSe) two years later and gave it the name Freboldite after the German geologist Georg Frebold (1891–1948).

A storage location for the type material of the mineral is not known (as of 2020).

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the Freboldite belonged to the mineral class of "sulfides and sulfosalts" and there to the division of "sulfides with [the molar ratio ] M (metal): S (sulfur) r = 1: 1", where he together with Achávalit (Achavalit) Breithauptit , Imgreit (discredited) Jaipurit , Kotulskit , Langisit , Nickelin , pyrrhotite , Sederholmit , Smythit and troilite the "NiAs-series" with the system number. II / B.09a .

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. II / C.20-40 . In the "Lapis system" this corresponds to the section "Sulphides with [the molar ratio] metal: S, Se, Te ≈ 1: 1", where Freboldite together with Breithauptite, Hexatestibiopanickelite , Kotulskite, Langisite, Nickelin, Sederholmit, Sorosit , Stumpflite , Sudburyit and Vavřínit and in the notes to Cherepanovit , polarity , Ruthenarsenit , Sobolevskit and Wassonit the "Nickelin group" is (as of 2018).

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also classifies Freboldite in the category of "Metal sulfides, M: S = 1: 1 (and similar)". However, this is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "with nickel (Ni), iron (Fe), cobalt (Co) etc.", where it can be found together with Achávalit , Breithauptit, Hexatestibiopanickelit , Jaipurit , Kotulskit , Langisit , Nickelin, Sederholmit, Sobolevskit, Stumpflit , Sudburyit , Vavřínit and Zlatogorit the "nickelin group" with the system no. 2.CC.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Freboldite to the class of "sulfides and sulfosalts" and there to the department of "sulfide minerals". Here it is in the " Nickelin group (hexagonal: P6 3 / mmc) " with the system no. 08/02/11 within the subsection of "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 1".

Chemism

The idealized (theoretical) composition of Freboldite (CoSe) consists of cobalt (Co) and selenium (Se) in a molar ratio of 1: 1. This corresponds to a mass fraction of 42.74% Co and 57.26% Se.

Crystal structure

Freboldite crystallizes isotypically with nickel line (see also nickel arsenide structure ) in the hexagonal crystal system in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a  = 3.63  Å and c  = 5.30 Å and two formula units per Unit cell . Template: room group / 194

properties

With a Mohs hardness of 5 to 5.5, Freboldite is one of the medium-hard minerals that, if the size is appropriate, could just about be scratched with a pocket knife, similar to the reference mineral apatite (hardness 5) .

Due to the small sample size, the density of Freboldite could not be determined by measurement up to now, but was calculated based on the crystal structure data. The calculated density is 7.70 g / cm 3 .

Education and Locations

Freboldit forms in dolomite - veins , where he usually fused with Clausthalit occurs. Other accompanying minerals include Bornhardtite, Chalcopyrite , Guanajuatite , Hematite , Hastite, Millerite , Nickelin, Sphalerite and Trogtalite.

In addition to its type locality in the Grauwacke quarry Trogtal near Lautenthal in Lower Saxony with selenium-bearing dolomite veins and iron ores, the mineral could also be found in Germany near Tilkerode in the district of Mansfeld-Südharz in Saxony-Anhalt.

Worldwide, the uranium - deposit Pinky Fault in the Canadian province of Saskatchewan and the Temple Mountain in the mining district of San Rafael in Emery County of the US state of Utah so far only two other localities for Freboldit known (as of 2020).

See also

literature

  • Paul Ramdohr , M. Schmitt: Four new natural cobalt selenides from the Trogtal quarry near Laufenthal in the Harz Mountains . In: New yearbook for mineralogy, monthly books . 1955, p. 133-142 .
  • Michael Fleischer : New mineral names . In: American Mineralogist . tape 41 , 1956, pp. 163–168 (English, rruff.info [PDF; 326 kB ; accessed on August 7, 2020]).
  • Hugo Strunz : Mineralogical tables . 3. Edition. Geest & Portig, Leipzig 1957, p. 98 (NiAs-type and related: Freboldite).
  • Michael Fleischer: New mineral names . In: American Mineralogist . tape 44 , 1959, pp. 906–910 (English, rruff.info [PDF; 377 kB ; accessed on August 7, 2020]).
  • Paul Ramdohr : The ore minerals and their adhesions . 4th, revised and expanded edition. Akademie-Verlag, Berlin 1975, p. 660 .

Web links

Individual evidence

  1. ↑ 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.  85 (English).
  2. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: July 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, July 2020, accessed August 7, 2020 .
  3. ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  191 .
  4. ↑ a b c d e Stefan Weiss: The great 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 .
  5. ↑ a b c d Freboldite . 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; 58  kB ; accessed on August 7, 2020]).
  6. ↑ Frank N. Keutsch, Hans-Jürgen Förster, Chris J. Stanley, Dieter Rhede: The discreditation of hastite, the orthorhombic dimorph of CoSe 2 , and observations on trogtalite, cubic CoSe2, from the type locality . In: The Canadian Mineralogist . tape 47 , 2009, p. 969–976 (English, rruff.info [PDF; 1,2 MB ; accessed on August 7, 2020]).
  7. ^ Hugo Strunz : Mineralogical tables . 3. Edition. Geest & Portig, Leipzig 1957, p.  98 (NiAs-type and related: Freboldite).
  8. ↑ Ernest H. Nickel , Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed August 7, 2020 .
  9. ↑ Freboldit. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on August 7, 2020 .
  10. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  447 (first edition: 1891).
  11. ↑ Michael Fleischer : New mineral names . In: American Mineralogist . tape  41 , 1956, pp. 163–168 (English, rruff.info [PDF; 326 kB ; accessed on August 7, 2020]).
  12. ↑ Find location list for Freboldite in the Mineralienatlas and Mindat , accessed on August 7, 2020.