Butcherite

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Butcherite
General and classification
chemical formula
  • Pb 3 Ge 4+ [(OH) 6 | (SO 4 ) 2 ] • 3H 2 O
  • Pb 3 Ge 4+ (SO 4 ) 2 (OH) 6 • 3H 2 O
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates, tungstates)
System no. to Strunz
and to Dana 		7.DF.25 ( 8th edition : VI / D.11)
07/31/06/03
Similar minerals Aragonite, dundasite
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol ditrigonal-dipyramidal; 6 m 2
Space group P 6 2 c (No. 190)Template: room group / 190
Lattice parameters a  = 8.87  Å ; c  = 10.87 Å
Formula units Z  = 2
Frequent crystal faces {11 2 0}, {0001}
Physical Properties
Mohs hardness "Soft", 2.5 to 3
Density (g / cm 3 ) 4.2-4.4 (measured); 4.59 (calculated)
Cleavage no
Break ; Tenacity not specified; brittle
colour white to pale pink, colorless in the shining light
Line color White
transparency transparent
shine Semi-glass gloss, silk gloss (in aggregates)
Crystal optics
Refractive indices n ω  = 1.747
n ε  = 1.776
Birefringence δ = 0.029
Optical character uniaxial positive
Other properties
Special features Rapid discoloration to pink-violet without any other visible change on exposure to X-rays. Fleischerite is clearly piezoelectric.

Fleischerite is a very rarely occurring mineral from the mineral class of the " sulphates , including selenates , tellurates , chromates , molybdates and tungstates ". It crystallizes in the hexagonal crystal system with the chemical formula Pb 3 Ge [(OH) 6 | (SO 4 ) 2 ] · 3H 2 O, so from a chemical point of view it is a water-containing lead - germanium- sulfate with additional hydroxide ions .

Fleischerite forms prismatic to fibrous crystals up to 1.5 cm in length, which can typically come together to form rounded, loosely matted aggregates up to 4 cm in diameter. Macroscopically, the aggregates appear silky-white, while dense bundles, viewed in sunlight on transverse breaks, reveal a pink hue. The mineral was formed by the alteration of germanium- and lead-rich primary sulfides.

Etymology and history

Samples of the mineral were collected in 1957 by Professor Hugo Strunz from the Tsumeb deposit. In the same year, the first chemical and optical data on the new mineral, which was also used in the investigation of certain germanium minerals such as B. stottite was observed, reported. After further research, Clifford Frondel and Hugo Strunz published the first description of the new mineral in the New Yearbook for Mineralogy, monthly books. They named it in honor of chemist and mineralogist Michael Fleischer of the United States Geological Survey .

Type material of the mineral is at the Technical University of Berlin (holotype, Collection no. 57/1405 on the site 23-3), at the national École supérieure des Mines de Paris , France (Cotyp), and the Smithsonian Institution belonging to the National Museum of Natural History , Washington, DC (Catalog No. 115310), retained.

classification

Already in the now outdated, but still in use 8th edition of the mineral systematics according to Strunz , the fleischerite belonged to the mineral class of "sulfates, chromates, molybdates, tungstates" and there to the department of "anhydrous sulfates, with foreign anions ", where it together with despujolsite , Mallestigit and Schaurteit the Schaurteit group with system no. VI / D.11 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 classifies Fleischerit as “sulfates (selenates, etc.) with additional anions, with H 2 O”. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section "With large and medium-sized cations" , where, together with despujolsite, mallestigite and schaurteit, the fleischerite group with the system No. 7.DF.25 forms.

The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns fleischerite to the class of “sulfates, chromates and molybdates” and there to the “hydrated sulfates with hydroxyl or halogen” class. Here it is together with Schaurteit, Despujolsit and Mallestigit in the Despujolsitgruppe with the system no. 07/31/06 within the subdivision of " Water-containing sulphates with hydroxyl or halogen with (A + B 2+ ) 2 (XO 4 ) Z q  • x (H 2 O) ".

Chemism

Fleischerit has (on the basis of 11 oxygen atoms per formula) the measured composition Pb 2.64 (Ge 0.93 Ga0 , 09 ) Σ = 1.02 (SO 4 ) 1.88 (OH) 5.91 · 3,47H 2 O, which was idealized to Pb 3 Ge (SO 4 ) 2 (OH) 6 • 3H 2 O and 15.36% SO 3 , 64.23% PbO, 10.04% GeO 2 and 10.37% H 2 O requires.

Fleischerite is the lead- dominant analogue of the calcium-dominated Schauteit , Ca 3 Ge (SO 4 ) 2 (OH) 6 · 3H 2 O, and the Pb-Ge-dominant analogue of the Ca-Mn-dominated despujolsite, Ca 3 Mn (SO 4 ) 2 (OH) 6 3H 2 O or to the Ca-Sn-dominated genplesite , Ca 3 Sn (SO 4 ) 2 (OH) 6 3H 2 O. Although showteit and fleischerite both occur in the Tsumeb deposit, there is no solid solution formation ( Substitution between Pb and Ca) known for these minerals.

Crystal structure

Fleischerite crystallizes hexagonally in the space group P 6 2 c (space group no. 190) with the lattice parameters a  = 8.87  Å and c  = 10.87 Å as well as two formula units per unit cell . Template: room group / 190

The framework of the fleischerite structure is formed by two Ge (OH) 6 coordination polyhedra lying one above the other in the direction of the c-axis , which are held together by Pb 2+ . Ge 4+ surrounds itself in an almost octahedral coordination with oxygen ligands. The true symmetry of the polyhedron differs only slightly from that of an ideal octahedron and is a trigonal trapezoid . Lead is 9-fold coordinated , with eight bonds pointing into the corners of a distorted tetragonal antiprism, which is formed by 4 OH - , 2 H 2 O and 2 oxygen atoms from the sulfate groups. Pb is linked via SO 4 groups which - in contrast to despujolsite - are disordered in the c-direction [001].

Despujolsite and Schaurteit and possibly also mallestigite are isotypic or isostructural to fleischerite.

properties

morphology

Fleischerite forms long prismatic, needle-like crystals, the shape of which is the prism {10 1 0} which determines the costume . Although the prisms are often broken off at their ends, the base pinacoid [0001] and / or a hexagonal pyramid can be identified as the end faces. Originally, the maximum length of fleischerite crystals was given as 0.5 mm and the thickness 0.03 mm, but today crystals up to 1.5 cm in length are known. Probably the world's best specimen shows a 3 cm large, tufted aggregate of 1.5 cm long, needle-like crystals.

physical and chemical properties

The color of the fleischerite crystals is white to - in sunlight on transverse fractures - pale pink. Due to the high dispersion, they can also appear in various other shades. The larger the crystals are and the closer they are grown together, the more intense the pink to rose-red color. The line color of the fleischerite crystals, however, is always white. When exposed to X-rays, the color quickly changes to pink-violet without any other changes being discernible. The surfaces of the transparent crystals have a glass-like to silk-like sheen , which corresponds to the relatively high birefringence of the mineral. Fleischerit is colorless and transparent in light transmitted through it.

No cleavage was found in the crystals of the fleischerite, and there is no information on the breakage . The mineral, described as brittle, has a Mohs hardness of 2.5 to 3 and is therefore one of the soft minerals that are slightly easier to scratch with a copper coin than the reference mineral calcite . The measured density for Fleischerite is 4.2-4.4 g / cm³, the calculated density for the mineral is 4.59 g / cm³. The mineral is clearly piezoelectric. Fleischerite is converted into Itoite after prolonged pulverization in an agate mortar when air is exposed or by heating to approx. 200 ° C with loss of water . Since pseudomorphoses from Itoite to Fleischerite exist, this phase change also takes place in nature. Although the natural pseudomorphization of fleischerite by itoite and thus the existence of itoite as an independent mineral has been questioned, itoite is considered a valid mineral in the sense of the IMA.

In optical determinations with immersion liquids , the mineral is not attacked by methylene iodide , but very quickly by liquids with a higher refractive index as soon as they contain arsenic bromide .

Education and Locations

Fleischerite arises as a typical secondary formation in the vicinity of germanium-containing polymetallic ore deposits . Lead and germanium come from the decomposition of former sulphidic ore minerals. When it was first found, the mineral sits in a matted aggregate 4 cm in diameter together with cerussite , small mimetite crystals and sooty-looking tennantite granules on a matrix of weathered tennantite. The second find consisted of fine fleischerite coatings and approaches on a lawn of green plumbojarosite and numerous pale olive-green mimetite crystals, all on a matrix of dolomite . Probably the best specimen shows an approximately 3 cm large, tufted aggregate of up to 1.5 cm long fleischerite crystals. Other accompanying minerals are angelsite , melanotekite , kegelite , alamosite , itoite and germanium- rich plumbogummite . Itoite forms fine-grained pseudomorphoses after Fleischerite. Much of the butchery of the collections is misidentified and has been found to be dundasite .

As a very rare mineral formation, Fleischerite could only be described from two sources so far (as of 2016). The type locality of the meatite is the first oxidation zone (probably one of the levels 6 to 8, which correspond to a depth of 150 to 200 m) of the world-famous Cu-Pb-Zn-Ag-Ge-Cd deposit of the "Tsumeb Mine" (Tsumcorp Mine ) in Tsumeb , Oshikoto Region , Namibia .

The antimony deposit of the "Llapa Llapa Mine" in the Bolivian Andes, Tomás Frías Province , Potosí Department , became known as the second site in the world. Fleischerite was found here in antimony mineralized tunnels in black schist together with alunite , jarosite and despujolsite in the spaces between quartz grains.

use

Due to its rarity, fleischerite is a mineral that is highly sought after by collectors.

See also

literature

  • Butcherite . 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; 67 kB ; accessed on October 19, 2017]).
  • Clifford Frondel , Hugo Strunz : Fleischerite and ltoite, two new germanium minerals from Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1960 , 1960, pp. 132-142 .
  • 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 , p. 160-190 .

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.  408 .
  2. ↑ a b c Fleischerite . 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; 67  kB ; accessed on October 19, 2017]).
  3. ↑ a b c d e f g h i j k l Clifford Frondel, Hugo Strunz: Fleischerit and ltoit, 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 Mindat - mineral description Fleischerit
  5. ↑ a b Type mineral catalog Germany - storage of the holotype stage Fleischerit
  6. ^ Clifford Frondel, Jun Ito: Geochemistry of Germanium in the oxidized zone of the Tsumeb Mine, South-West Africa . In: The American Mineralogist . tape 42 , 1957, pp. 743-753 .
  7. ↑ Catalog of Type Mineral Specimens - F. (PDF 73 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  8. ↑ a b c Marcus J. Origlieri, Robert T. Downs: Schaurteite, Ca 3 Ge (SO 4 ) 2 (OH) 6 · 3H 2 O . In: Acta Crystallographica . E69, 2013, p. i6 and sup-1 to sup-7 , doi : 10.1107 / S1600536812050945 ( rruff.info [PDF; 681 kB ; accessed on October 19, 2017]).
  9. ↑ a b c d e f Hermann H. 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 , 1975, pp. 160-190 .
  10. ↑ Madison C. Barkley, Hexiong Yang, Stanley H. Evans, Robert T. Downs, J. Marcus Origlieri: Redetermination of despujolsite, Ca 3 Mn 4+ (SO 4 ) 2 (OH) 6 · 3H 2 O . In: Acta Crystallographica . E67, 2011, p. i47 – i48 , doi : 10.1107 / S1600536811030911 ( rruff.info [PDF; 1.1 MB ]).
  11. ↑ a b c Georg Gebhard: Tsumeb. A German-African story . 1st edition. Gebhard-Giesen, Obernwehnrath 1991, p. 193 .
  12. ^ IMA / CNMNC List of Mineral Names; May 2016 (PDF, 1.6 MB)
  13. ↑ Georg Gebhard: Tsumeb. A German-African story . 1st edition. Gebhard-Giesen, Obernwehnrath 1999, p. 275 .
  14. ↑ Mindat - Examples of incorrect determination of dundasite and aragonite as fleischerite
  15. ↑ Mindat - Number of localities for Fleischerit
  16. ↑ a b List of localities for fleischerite in the Mineralienatlas and Mindat
  17. ↑ Harald G. Dill: Evolution of Sb mineralization in modern fold belts: a comparison of the Sb mineralization in the Central Andes (Bolivia) and the Western Carpathians (Slovakia) . In: Mineralium Deposita . tape 33 , 1998, pp. 359-378 , doi : 10.1007 / s001260050155 .