Itoit

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Itoit
General and classification
chemical formula
  • Pb 3 Ge 4+ O 2 (SO 4 ) 2 (OH) 2
  • Pb 3 [GeO 2 (OH) 2 | (SO 4 ) 2 ]
  • Pb 3 [GeO 2 (OH) 2 (SO 4 ) 2 ]
  • Pb [(S, Ge) (O, OH) 4 ] with (SO 4 ): (GeO 2 (OH) 2 ) = 2: 1
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates and tungstates)
System no. to Strunz
and to Dana 		7.BD.50 ( 8th edition : VI / B.08)
02/30/06/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnma (No. 62)Template: room group / 62
Lattice parameters a  = 8.47  Å ; b  = 5.38 Å; c  = 6.94 Å
Formula units Z  = 4
Physical Properties
Mohs hardness no information as it cannot be determined
Density (g / cm 3 ) 6.67 (calculated)
Cleavage no
Break ; Tenacity brittle
colour white, colorless in transmitted light
Line color White
transparency transparent
shine Silky gloss
Crystal optics
Refractive index n  = 1.84 to 1.85
Optical character biaxial, orientation unknown
Pleochroism not pleochroic

Itoite is an extremely rarely occurring mineral from the mineral class of " sulfates (and relatives, see classification)". It crystallizes in the orthorhombic crystal system with the idealized composition Pb 3 Ge 4+ O 2 (SO 4 ) 2 (OH) 2 , so it is chemically seen a lead - germanium - sulfate with additional groups of the form [GeO 2 (OH) 2 ] 2 - .

Itoite is a typical secondary mineral and was created as a pseudomorphic conversion product from fleischerite through oxidation of germanium and simultaneous loss of water. It forms a very fine-grained mixture with aggregate polarization.

The type locality for Itoit is the so-called first oxidation zone of the Tsumeb Mine near Tsumeb , Oshikoto Region , Namibia .

Etymology and history

In the course of the investigation of the geochemistry of germanium in the upper (first) oxidation zone of the germanium-rich copper, lead and zinc deposits of Tsumeb in SW Africa, Clifford Frondel and June Ito (1957) briefly named an obviously new germanium-containing basic lead sulfate. The same mineral was found when studying special germanium minerals such as B. stottite observed. Occasionally it is represented pseudomorphically by another new mineral. The first mineral is fleischerite , the first scientific description of which, written by Clifford Frondel and Hugo Strunz , was published in 1960 in the German scientific magazine "New Yearbook for Mineralogy, MONTHS". The second mineral was described in the same publication as Itoite ( English Itoite ). The authors named it after the professor of mineralogy and crystallography at the Institute of Mineralogy at Tokyo University Tei-ichi Ito (1898–1980). The mineral was unanimously recognized as a new mineral by the International Mineralogical Association (IMA) in 1960 - together with and like Fleischerite .

Type material for the mineral is kept at the Technical University of Berlin (holotype, collection no. 57/1405 at location 23-3). It is a fine-grain coating of fleischerite and itoite on a lawn of plumbojarosite next to mimetite on dolomite and 60 mg of loose powder. Another type of material is in the collection of the Harvard University in Cambridge ( Massachusetts ), United States , and in the Smithsonian Institution belonging to National Museum of Natural History , Washington, DC (catalog no. 162597). According to the former curator of the Harvard University collection, Carl Francis, the itoite crystals have a cloudy appearance compared to the transparent fleischerite. The investigations by Frondel and Strunz have already made it clear that the refractive indices of Itoite are much higher than those of Fleischerit. The Harvard type material is probably a mixture of itoite and fleischerite.

Years later, as a result of his investigations, Hans Hermann Otto pointed out that Itoite “is not a homogeneous phase and should be painted as a mineral. Itoite is a pseudomorphic conversion product according to Fleischerite and contains at least one other phase in addition to angelsite. Building on this, Paul Ramdohr and Hugo Strunz stated that “it is a pseudomorphism of angelsite and amorphous PbGeO 3 or crystallized PbGe 2 O 5 according to Fleischerite”. Logically, the "mineral" Itoite either no longer appears in all important publications on the mineralogy of the Tsumeb deposit or is mentioned as an invalid mineral that is to be deleted.

However, the mineral has never been formally discredited. In the current list of the IMA, the Itoit is listed as "recognized".

classification

Already in the meanwhile outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the itoite belonged to the mineral class of "sulfates, selenates, tellurates, chromates, molybdates, wolframates" and there to the department of "anhydrous sulfates with foreign anions ", where together with Sidpietersit the independent group with the system no. VI / B.08 .

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 itoite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and there in the department of “Sulphates (selenates etc.) with additional anions, without H 2 O”. However, this section is further subdivided according to the size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With only large cations”, where it is the only member of the unnamed group with system no. 7.BD.50 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns itoite to the class of "sulfates, chromates and molybdates" and there to the category of "anhydrous sulfates with hydroxyl or halogen". Here he is to be found as the only member of the unnamed group 02/30/06 within the sub-section " Anhydrous sulfates with hydroxyl or halogen with (AB) 2 XO 4 Z q ".

Chemism

Frondel and Strunz only report on the results of a qualitative analysis of Itoite, as a result of which the presence of lead, germanium and sulfate was determined. According to the qualitative analysis, the germanium is in the tetravalent oxidation state, which is why the formula must contain Pb: Ge 4+  : SO 4 in the same ratio as in Fleischerite, i.e. in a ratio of 3: 1: 2.

Since the powder diagram of natural Itoite largely corresponds to that of Anglesite , the formula of Itoite corresponds to Pb 3 [GeO 2 (OH) 2 (SO 4 ) 2 ], i.e. that of an Anglesite in which a third of the [SO 4 ] 2− - Tetrahedra are represented by tetrahedra of the form [GeO 2 (OH) 2 ] 2− . From the great agreement between the X-ray diagrams of Itoite and that of Anglesite, Frondel and Strunz conclude that the tetrahedron mentioned is represented statistically, that is, the simplified formula for Itoite is Pb [(S, Ge) (O, OH) 4 ] (SO 4 ): (GeO 2 (OH) 2 ) = 2: 1.

In 1960, Itoite was the sixth mineral in the world and the fourth mineral for the "Tsumeb Mine" with germanium as an active ingredient in the formula. Of the 33 germanium-containing minerals known worldwide today, 18 occur in the "Tsumeb Mine", 14 of these 33 minerals, almost half, were also described for the first time from the "Tsumeb Mine".

Crystal structure

Itoite crystallizes orthorhombically in the space group Pnma (space group no. 62) with the lattice parameters a  = 8.47  Å ; b  = 5.38 Å and c  = 6.94 Å as well as four formula units per unit cell . Template: room group / 62

The crystal structure of itoite corresponds to the barite structure type, so the two minerals barite and itoite are isotypic (isostructural). The powder diagram of natural Itoite largely corresponds to that of Anglesit and corresponds to that of Fleischerit heated to 300 ° C.

properties

morphology

Itoite is a pseudomorphic conversion product of fleischerite and sits with it as a hint on the accompanying minerals. Under the microscope he shows the forms of this starting mineral known for fleischerite, namely elongated hexagonal prisms {11 2 0} or {10 1 0} with end faces that go back either to the basic pinacoid {0001} or a hexagonal pyramid. Usually, however, the elongated Fleischerit prisms are broken off irregularly at their ends.

physical and chemical properties

The pseudomorphoses from Itoit to Fleischerit are white, the streak color of the mineral is also always white. The surfaces of the transparent Itoite show a silky sheen , which agrees well with the value for the mean refraction . This value is 1.84 to 1.85. In transmitted light, itoite is colorless and not pleochroic.

Itoite has no cleavage properties and is brittle, although no information is available on tenacity . There is also no information on the Mohs hardness , as it obviously cannot be determined from the pseudomorphoses. The calculated density for Itoite is 6.67 g / cm³. Itoit is neither in the long term nor in the short wavelength UV light , a fluorescent .

Education and Locations

As a very rare mineral formation, Itoite could only be described from one site so far (as of 2018). The type locality is the "Tsumeb Mine" near Tsumeb, Oshikoto region , Namibia , the exact location within the mine being on levels 6 to 8 (corresponding to a depth of 150 to 200 m) in the area of ​​the first oxidation zone. Itoite occurrences in Germany , Austria or Switzerland are therefore not known.

Itoit is a typical secondary mineral , which in the oxidation zone an arsenic-rich polymetallic non-ferrous metal - deposit has formed. Itoite occurs in Tsumeb together with fleischerite as a touch on green plumbojarosite and numerous pale olive-green mimetite crystals on a matrix of dolomite . It was formed from fleischerite through oxidation of germanium and simultaneous loss of water, as Frondel and Strunz assume according to the following equation: Pb 3 Ge 2+ [(OH) 4 | (SO 4 ) 2 ] · 4H 2 O + ½O 2 → Pb 3 [Ge 4+ O 2 (OH) 2 (SO 4 ) 2 ] + 5H 2 O. Frondel and Strunz already point out that itoite is also formed after prolonged pulverization of fleischerite in an agate mortar when exposed to air.

According to Hans Hermann Otto, however, Itoite is not a homogeneous phase and should be painted as a mineral. As Frondel and Strunz already formulated it, it is a pseudomorphic conversion product according to Fleischerite and contains at least one other phase in addition to angelsite. However, this view has not prevailed as itoite is still considered a recognized mineral.

use

Due to its rarity, itoite is a sought-after mineral by mineral collectors, but otherwise of no practical importance.

See also

literature

  • Clifford Frondel, Hugo Strunz: Fleischerite and Itoite, two new germanium minerals from Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1960 , 1960, pp. 132-142 .
  • Itoite . 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 July 31, 2018]).
  • 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. 682 .
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 601 (first edition: 1891).

Web links

Individual evidence

  1. ↑ a b c d IMA / CNMNC List of Mineral Names; March 2018 (PDF 1.65 MB)
  2. ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  379 .
  3. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab Clifford Frondel, Hugo Strunz: Fleischerit and Itoite, two new germanium minerals from Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1960 , 1960, pp. 132-142 .
  4. ↑ a b c d e f g h i j k l m Mindat - Itoit
  5. ↑ a b c Itoite . In: 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 July 31, 2018]).
  6. ^ Clifford Frondel, Jun Ito: Geochemistry of Germanium in the oxidized zone of the Tsumeb Mine, South-West Africa . In: American Mineralogist . tape 42 , no. 11-12 , 1957, pp. 734-747 ( minsocam.org [PDF; 760 kB ; accessed on July 31, 2018]).
  7. ↑ Hugo Strunz, Gerhard Söhnge, Bruno H. Geier: Stottite, a new germanium mineral, and its paragenesis in Tsumeb . In: New Yearbook Mineralogy, monthly books . tape 1957 , 1957, pp. 85-96 .
  8. ↑ International Mineralogical Association: Commission on New Minerals and Mineral Names: Without . In: Mineralogical Magazine . tape 33 , no. 3 , 1982, pp. 260–263 ( rruff.info [PDF; 150 kB ; accessed on July 31, 2018]).
  9. ↑ Type mineral catalog Germany - storage of the holotype stage Itoit
  10. ↑ a b c d Hans Hermann Otto: The crystal structure of Fleischerite, Pb 3 Ge [(OH) 6 | (SO 4 ) 2 ] · 3H 2 O, as well as crystal chemical investigations on isotypic compounds . In: New Yearbook for Mineralogy, Treatises . tape 123 , 1977, pp. 160-190 .
  11. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  601 (first edition: 1891).
  12. ^ Paul Keller, Wolfgang Bartelke: Tsumeb! New minerals and their associations . In: The Mineralogical Record . tape 13 , no. 3 , 1982, pp. 137-147 .
  13. ↑ Paul Keller: Tsumeb / Namibia - one of the most spectacular mineral discovery sites on earth . In: Lapis . tape 9 , no. 7-8 , 1984, pp. 13-62 .
  14. ^ Georg Gebhard: Tsumeb - a German-African story . 1st edition. Verlag Gebhard-Giesen, Reichshof 1991, p. 1-239 .
  15. ^ Georg Gebhard: Tsumeb II. A Unique Mineral Locality . 1st edition. GG Publishing, Grossenseifen 1991, p. 1-328 .
  16. ↑ Wolfgang Bartelke: The ore deposit of Tsumeb / South West Africa and its minerals . In: The opening . tape 27 , no. 12 , 1975, p. 393-439 .
  17. ↑ William W. Pinch, Wendell W. Wilson: Minerals: a descriptive list . In: The Mineralogical Record . tape 8 , no. 3 , 1977, pp. 17-37 .
  18. ^ Vaughan DC Daltry: Type Mineralogy of Namibia . In: Geological Survey of Namibia Bulletin . tape 1 , 1992, ISBN 978-0-86976-254-7 , pp. 62 .
  19. ↑ Michael Fleischer: New Mineral Names. Fleischerite, Itoite . In: American Mineralogist . tape 45 , no. 11-12 , 1960, pp. 1313-747 ( rruff.info [PDF; 373 kB ; accessed on July 31, 2018]).
  20. ↑ Mindat - Number of localities for Itoit
  21. ↑ a b List of localities for Itoite in the Mineralienatlas and Mindat
  22. ↑ Tsumeb.com - Itoite (English)