Penroseit

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Penroseit
Penro-page-217412.jpg
Penroseit from the “Virgen de Surumi” mine, Pakaja Canyon, Chayanta , Potosí Department , Bolivia
General and classification
other names

Blockit

chemical formula
  • (Ni, Co, Cu) Se 2
  • NiSe 2
Mineral class
(and possibly department) 		Sulphides and sulphosalts (including selenides, tellurides, arsenides, antimonides and bismuthides)
System no. to Strunz
and to Dana 		2.EB.05a ( 8th edition : II / C.05)
02.12.01.04
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-disdodecahedral; 2 / m  3
Space group Pa 3 (No. 205)Template: room group / 205
Lattice parameters a  = 5.96  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 5.5–6 or 3 ( VHN 100  = 500–583 or 407 to 550 kg / mm 2 )
Density (g / cm 3 ) measured: 6.58 to 6.74; calculated: 6.7
Cleavage completely after {001}, clearly after {011}
Break ; Tenacity slightly mussel-like; brittle
colour lead gray, polished: creamy white gray
Line color black
transparency opaque (opaque)
shine Metallic luster
Other properties
Chemical behavior very soluble in nitric acid

Penroseit , also synonymous with blockite , is a rarely occurring mineral from the mineral class of " sulfides " and " sulfosalts " with the idealized chemical composition NiSe 2 and thus, chemically speaking, nickel diselenide . As close relatives of the sulfides, the selenides are placed in the same class.

Penroseit crystallizes in the cubic crystal system , but develops only microscopic crystals and is mainly found in the form of kidney-shaped, massive mineral aggregates with a radial, columnar structure. Penroseite in any form opaque ( opaque ). Fresh penoside samples are lead-gray, on polished surfaces also creamy-white-gray in color and show a metallic sheen on the surfaces. However, these start up very quickly.

Etymology and history

The mineral was described in 1926 by Samuel George Gordon after a find from Colquechaca in Bolivia , who named it after the American mineralogist Richard Alexander Fullerton Penrose, Jr. (1863-1931).

Penroseit was the first natural nickel selenide to be discovered and at the time also the mineral with the highest selenium content. In 1935 the selenium content was exceeded with Blockit, described by Robert Herzenberg and Friedrich Ahlfeld . Already two years later, however, FA Bannister and Max H. Hey recognized on the basis of their analyzes that, apart from minor fluctuations in the foreign admixtures, blockite is identical to penrosite due to the same symmetry and crystal structure.

The type material of the mineral is in the Natural History Museum in London, England under the catalog no. 1926.1 , Harvard University in Cambridge, Massachusetts under catalog no. 87472 and in the National Museum of Natural History in Washington, DC, USA under catalog no. 95302 and R7247 kept.

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the penrosite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with M: S <1: 1", where together with Aurostibit , Cattierit , Geversit , Hauerit , Laurite , michenerite , pyrite , sperrylite , trogtalite , vaesite and villamanínite the "pyrite series" with the system no. II / C.05 formed.

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 / D.17-90 . In the "Lapis system" this also corresponds to the section "Sulphides with metal: S, Se, Te <1: 1", where Penroseit together with Aurostibit, Cattierit, Changchengit , Dzharkenit , Erlichmanit , Fukuchilit , Geversit, Hauerit, Insizwait , Krutaite , Laurit, Maslovit , Mayingit , Michenerit, Padmait , pyrite, Sperrylith, Trogtalit, Testibiopalladit , Vaesit and Villamanínit the "pyrite group" formed (as 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies the Penroseit in the more general section of “Metal sulfides with M: S ≤ 1: 2”. However, this is further subdivided according to the exact molar ratio and the predominant metals in the compound, so that the mineral can be found according to its composition in the subsection "M: S = 1: 2, with Fe, Co, Ni, PGE etc." where it together with Aurostibit, cattierite, Dzharkenit, Erlichmanit, Fukuchilit, Gaotaiit , Geversit, Hauerit, Insizwait, Iridisit , Krutaite, Laurit, pyrite, Sperrylith, Trogtalit, Vaesit and Villamanínit the "pyrite group" with the system no. 2.EB.05a forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Penroseit to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it is also in the "pyrite group (isometric: Pa 3 )" with the system no. 02.12.01 to be found within the subsection “ Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2 ”. Template: room group / 205

Chemism

According to the idealized (theoretical) composition of penroseite (NiSe 2 ), the mineral consists of 27.09% nickel and 72.91% selenium . Analysis of the type material from Bolivia and from the transition - deposit Hope's Nose in Torquay , however, in the English county of Devon were additional levels of 3.2 and 9.2% cobalt and 2.1 and 5.7% copper , the corresponding one Replace part of the nickel ( substitution , diadochy).

The empirical formula (Ni 0.84 Co 0.12 Cu 0.07 ) Σ = 1.03 Se 1.97 or (Ni 0.46 Co 0.34 Cu 0.20 ) Σ = results from the results 1.00 Se 2.00 , which has been idealized for the mixed formula (Ni, Co, Cu) Se 2 and is specified by the IMA as the official formula for the Penroseit.

In addition, lead contents of up to 17% as well as small additions of silver (1.73–7.78%), mercury (1.41–4.12%) and iron (0.72–1.29% ) were found in various penroside samples. ) measured.

Crystal structure

Penroseit crystallizes cubically in the pyrite structure in the space group Pa 3 (space group no. 205) with the lattice parameter a  = 5.96  Å and four formula units per unit cell . Template: room group / 205

The crystal structure of penroseite corresponds to the pyrite structure , with nickel instead of iron atoms occupying the lattice sites of a face-centered cubic unit cell and dumbbell-shaped selenium 2 groups occupying the interstitial sites . The dumbbell axes are each aligned in different orientations parallel to the 3-fold axes of rotation, which is the reason for the lower symmetry class within the cubic system.

Crystal structure of penroseit

  • looking parallel to the a-axis

  • looking parallel to the b-axis

  • looking parallel to the c-axis

  • spatial representation centered on the three spatial diagonals

Color table: __ Ni     __ Se

properties

Penrosit dissolves very well in nitric acid (HNO 3 ) with effervescence . Other typical solvents such as hydrochloric acid (HCl), iron (III) chloride (FeCl 3 ), mercury (II) chloride (HgCl 2 ) and potassium hydroxide (KOH) show no change. Only with potassium cyanide (KCN) did a gray-brown discoloration develop.

There are different statements regarding the hardness of penroseit. The Mohs hardness is given as 3 by Gordon who first described it. Other sources indicate a Mohs hardness between 2.5 and 3 or 4 (according to ND Sindeeva 1964 also 4.7). The Vickers hardness (VHN) should be between 500 and 583 kg / mm 2 with a test force of 100 g , which according to Alexander Hölzel (1945–2012) would correspond to a Mohs hardness of 5.5 to 6. In the 1985 published work Tables for Microscopic Identification of Ore Minerals by Willem Uytenbogaardt (1918-2012) and Ernest Alexander Julius Burke , however, a lower Vickers hardness of 407 to 550 kg / mm 2 is given for Penroseit .

Education and Locations

Penroseit forms in hydrothermal rock veins . Have been observed assemblages with Naumannite , Clausthalit , Gersdorffit , Tiemannite , pyrite, chalcopyrite , Sederholmit and Trüstedtit .

Currently (2015) 16 sites are known from Penroseit. Four of them are in Germany .

In Germany there is a site in Bavaria in Wölsendorf ( Upper Palatinate ), one in Lower Saxony in Lautenthal ( Harz ), one in Rhineland-Palatinate in Niederfischbach ( Siegerland ) and one in Saxony-Anhalt in Abberode (also Harz).

There is also a locality in Bolivia, which is the type locality , two in China , two in Finland , one in Canada , one in the DR Congo , one in Romania , one in Spain and one in the United Kingdom .

See also

literature

  • Samuel G. Gordon: Penroseite and Trudellite: Two New Minerals . In: Proceedings of the Academy of Natural Sciences of Philadelphia . tape 77 , 1925, pp. 317-324 (English).
  • WF de Jong, HWV Willems: Connections FeSe 2 , CoSe 2 and NiSe 2 . In: Journal of Inorganic and General Chemistry . tape 170 , 1928, pp. 241–245 ( rruff.info [PDF; 188 kB ; accessed on April 8, 2020]).
  • Sigrid Furuseth, Arne Kjekshus: On the magnetic properties of CoSe 2 , NiS 2 and NiSe 2 . In: Acta chemica scandinavia . tape 23 , 1969, p. 2325–2334 (English, actachemscand.dk [PDF; 1,2 MB ; accessed on April 8, 2020]).
  • Peter Bayliss: Crystal chemistry and crystallography of same minerals within the pyrite group . In: American Mineralogist . tape 74 , 1989, pp. 1168–1176 ( minsocam.org [PDF; 1,2 MB ; accessed on April 8, 2020]).

Web links

Commons : Penro site  - 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: March 2020. (PDF; 1729 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed April 8, 2020 .
  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.  104 (English).
  3. ↑ a b c d e f g h i j k l penro page . 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; 62  kB ; accessed on April 8, 2020]).
  4. ↑ a b Stefan Weiß: Pyrite systematics. Pyrite and marcasite: an extended family . In: pyrite and marcasite. The iron everywhere mineral (= Christian Weise [Hrsg.]: ExtraLapis . Volume 11 ). Christian Weise Verlag, 1996, ISBN 3-921656-38-9 , ISSN  0945-8492 , p. 7 .
  5. ^ A b Samuel G. Gordon: Penroseite and Trudellite: Two New Minerals . In: Proceedings of the Academy of Natural Sciences of Philadelphia . tape 77 , 1925, pp. 317-324 (English).
  6. ↑ a b Penro page. In: mindat.org. Hudson Institute of Mineralogy, accessed April 14, 2020 .
  7. ↑ a b W. Uytenbogaardt, Ernest Alexander Julius Burke: Tables for Microscopic Identification of Ore Minerals . Courier Corporation, 1985, ISBN 0-486-64839-7 , pp. 23 (English, limited preview in Google Book Search).
  8. ↑ a b JW Earley: Description and synthesis of the selenide minerals . In: The American Mineralogist . tape 35 , no. 5-6 , 1950, pp. 360 (English, rruff.info [PDF; 1.9 MB ; accessed on April 8, 2020]).
  9. ↑ Robert Herzenberg, Friedrich Ahlfeld: Blockit, a new beer ore from Bolivia . In: Zentralblatt für Mineralogie, Geologie und Paläontologie . tape 6 , 1935, pp. 277–279 ( rruff.info [PDF; 223 kB ; accessed on April 12, 2020]).
  10. ↑ a b FA Bannister, Max H. Hey: The identity of penroseite and blockite . In: American Mineralogist . tape 22 , no. 5 , 1937, pp. 319–324 (English, minsocam.org [PDF; 417 kB ; accessed on April 8, 2020]).
  11. ↑ 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 .
  12. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 8, 2020 .
  13. ^ A b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  253 .
  14. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  459 (first edition: 1891).
  15. ↑ Paul Ramdohr : The ore minerals and their adhesions . 4th, revised and expanded edition. Akademie-Verlag, Berlin 1975, p.  877, 1218 .
  16. ↑ a b c List of locations for laurite in the Mineralienatlas and Mindat , accessed on April 8, 2020.