Krettnichit

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Krettnichit
General and classification
other names

IMA 1998-044

chemical formula PbMn 3+ 2 (VO 4 ) 2 (OH) 2
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.CG.15 ( 8th edition : VII / C.31)
10.41.07.02
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 9.275  Å ; b  = 6.284 Å; c  = 7.682 Å
β  = 117.97 °
Formula units Z  = 2
Frequent crystal faces {001}, {111}, {332}, {331}
Twinning polysynthetic according to (001)
Physical Properties
Mohs hardness 4.5, VHN 100  = 276 kg / mm 2 vertical (001), 347 kg / mm 2 || (001)
Density (g / cm 3 ) 4.51 to 4.81 (calculated)
Cleavage very perfect after {001}
Break ; Tenacity not given; not given
colour black or brownish, reddish brown in reflected light
Line color brown
transparency transparent in thin split plates
shine Diamond luster
Crystal optics
Refractive indices n α  = 2.210
n γ  = 2.390
Birefringence δ = 0.180
Optical character biaxial
Pleochroism weak from very light gray to light brownish gray
Other properties
Chemical behavior sensitive to alkalis
Special features Epitaxy of brackebushite on krettnichite crystals

Krettnichite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition PbMn 3+ 2 (VO 4 ) 2 (OH) 2 and is therefore chemically a lead - manganese - vanadate with two hydroxide ions .

At its type locality, Krettnichit develops radial aggregates with a maximum diameter of 3 cm, which consist of tabular crystals up to 1 mm in size. The type locality of the mineral are mining dumps at Krettnich southeast of Wadern in the district of Merzig-Wadern in northern Saarland , where he in cavities in the material from a hydrothermal manganite - quartz - transition occurred.

Etymology and history

As early as 1982 an “unknown Pb-Mn-Vanadate” was described from Krettnich and an X-ray diffraction diagram was published, but a complete characterization and description as a new mineral was omitted at that time. But it was not until May 1996 that new material of the unknown Pb-Mn vanadate was found on the edge of an old pinge . The mineral collectors Hartmut Hensel (Neustadt / Weinstrasse), Klaus Schäfer (Idar-Oberstein) and Thomas Raber (Neunkirchen / Saar) made samples of this material available, which the Swiss-Australian mineralogist Joël Brugger identified as a new representative of the tsumcorite group at the end of 1997. After the required further extensive investigations, the new phase was presented to the International Mineralogical Association (IMA), which recognized it as a new mineral in 1998 with the IMA number "1998-044". In 2001 the mineral was described by an international team of scientists led by Joël Brugger and Thomas Armbruster , Alan Criddle , Peter Berlepsch , Stefan Graeser and Shane Reeves in the international science magazine "European Journal of Mineralogy" under the name Krettnichit as Mn 3+ analogue of Mounanaite . The authors named the mineral after its type locality.

The type material for Krettnichit (type level) is kept under the catalog number MGL 65317 in the "Collection of the Musée cantonal de géologie de Lausanne" in Lausanne , Switzerland. The polished material from the type stage (bevel) is in the Natural History Museum in London , United Kingdom .

classification

The current classification of the International Mineralogical Association (IMA) counts the krettnichite to the tsumcorite group with the general formula Me (1) Me (2) 2 (XO 4 ) 2 (OH, H 2 O) 2 , in which Me (1), Me (2) and X different positions in the structure of the minerals of the tsumcorite group with Me (1) = Pb 2+ , Ca 2+ , Na + , K + and Bi 3+ ; Me (2) = Fe 3+ , Mn 3+ , Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ , Mg 2+ and Al 3+ and X = As 5+ , P 5+ , V 5+ and represent S 6+ . To Tsumcoritgruppe include not only Krettnichit still Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite .

Since the Krettnichit was only recognized as an independent mineral in 1998, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . Only 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 , was the mineral given the system and mineral number. VII / C.31-74 . In the "lapis system" this corresponds to the class of "phosphates, arsenates and vanadates" and there to the section "water-containing phosphates, without foreign anions ", where krettnichite together with cabalzarite, cobalt solder armeyerite, cobalt sumcorite, ferrilotharmeyerite, gartrellite, helmutwinklerite, lotharmeyerite, Lukrahnite, Manganlotharmeyerit, Mawbyit, Mounanait, Nickellotharmeyerit, Nickelschneebergit, Nickeltsumcorit, Phosphogartrellite, Rappoldit, Schneebergite, Thometzekit, Tsumcorite, Yancowinnait and Zinkgartrellite form the "Tsumcorite-Gartrellit-Gruppe 2018".

The 9th edition of Strunz's mineral systematics , which has been valid since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns krettnichite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral can be classified according to its composition in the subsection “With large and medium-sized cations; RO 4  : H 2 O = 1: 1 "is to be found, where together with Cabalzarite, Cobaltlotharmeyerite, Cobalttsumcorit, Ferrilotharmeyerit, Lotharmeyerit, Manganlotharmeyerit, Mawbyit, Mounanait, Nickellotharmeyerit, Nickelschneebergit, Schneebergite", Thometzekit and Tsumcorit the "Tsumcorite System no. 8.CG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns krettnichite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is together with Mounanait in the " Mounanait group " with the system no. 41.10.07 within the subsection “Anhydrous phosphates etc., with hydroxyl or halogen with (A 2+ B 2+ ) 3 (XO 4 ) 2 Z q ”.

Chemism

Twenty-four microprobe analyzes on Fe 3+ -free Krettnichite resulted in mean values ​​of 34.65% PbO; 0.42% CaO; 1.40% SrO; 0.55% BaO; 2.32% CoO; 0.04% NiO; 0.44% CuO; 23.29% MnO; 30.38% V 2 O 5 ; 2.36% As 2 O 5 and 3.33% H 2 O (calculated) as well as smaller amounts of Fe 2 O 3 (<0.05% by weight) and Al 2 O 3 (<0.03% by weight ). On the basis of ten oxygen atoms , the empirical formula was calculated from them (Pb 0.83 Co 0.17 Sr 0.08 Ca 0.06 Ba 0.03 Cu 0.03 ) Σ = 1.20 (Mn 1.73 Fe 0.09 ) Σ = 1.82 [(V 1.86 As 0.14 ) O 4 ] 1.97 (OH) 2.23 , which to PBMN 3+ 2 (VO 4 ) 2 (OH) 2 was idealized .

Theoretically, the presence of both hydroxide ions and water molecules is possible in the minerals of the tsumcorite group according to the coupled substitution [VI] Me 3+ (OH) - ↔ [VI] Me 2+ (H 2 O). However, since there are only trivalent cations in the Krettnichit on the Me (2) position, the O (1) position is occupied exclusively by (OH) - groups, a substitution by water molecules (H 2 O) is therefore not necessary.

Krettnichite is the Mn 3+ -dominant analogue of the Fe 3+ -dominant mounanaite. Krettnichite and mounanaite are the only two vanadates within the tsumcorite group.

Crystal structure

Crystal structure of krettnichite. Project in direction (104).

Krettnichite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 9.275  Å ; b  = 6.284 Å; c  = 7.682 Å and β = 117.97 ° as well as two formula units per unit cell . Template: room group / 12

The crystal structure of Krettnichite consists of Mn 3+ O 6 coordination octahedra , which are linked by common edges to form chains parallel [010]. VO 4 - Tetrahedra with common corners connect these chains, creating layers parallel to the ab-surface. The layers are connected by hydrogen bonds and by Pb [6 + 2] atoms. Mn in the Me (2) position is coordinated in an octahedral manner, the Mn 3+ O 6 octahedra are clearly distorted by the Jahn-Teller effect (compare the adjacent figures for the crystal structure).

Krettnichite is isotypic (isostructural) to those monoclinic minerals of the tsumcorite group, which crystallize in the space group C 2 / m (space group no. 12) . In addition to cabalzarite, cobalt solder armyerite, cobalt sumcorite, ferrilotharmeyerite, lotharmeyerite, manganese solder armyerite, mawbyite, mounanaite, nickellotharmeyerite, nickel schneebergite, nickel sumcorite, snow mountainite, Thometzekit and tsumcorite also natrochalcite and potash calcite. Template: room group / 12

properties

Costume and habitus of Krettnichit crystals (same colors represent the same surface shapes)
Krettnichit crystal drawing 1.png
Krettnichit crystal, normal setup
Krettnichit crystal drawing 2.png
same crystal, tilted 45 ° by [010]

morphology

At its type locality in the massive manganite ore, Krettnichit develops radial aggregates up to 3 cm in diameter, which consist of tabular-plate crystals with {001} as a supporting form. In cavities it forms tiny crystals up to a maximum of 1 mm in size. A distinction must be made between needle-like and prismatic, black crystals from brownish crystals with a pseudorhombohedral habit . On the crystals, which are often polysynthetically twinned with (001) as a twin surface, the prisms {111}, {332} and {331} are observed in addition to the basic pinacoid {001} (compare the crystal drawing opposite). The needle-like crystals seem to consist only of {001} and a prism {hk0}. However, Weissenberg photographs show that these “crystals” are composed of complex aggregates.

Epitaxial adhesions of krettnichite with brackish bushite are widespread, the b-axis of brackish bushite being oriented parallel to the b-axis of krettnichite. The b-axis [010] is the direction of the octahedral chains in both brackebushite and krettnichite. For this reason, the epitaxy is developed between the (102) face of the brackish bushite crystals and the (201) face of the krettnichite.

physical and chemical properties

The Krettnichite crystals are brownish or black, but their streak color is always brown. Orange-red internal reflections are characteristic. The surfaces of the transparent, otherwise opaque crystals have a diamond-like sheen , which corresponds well with the values ​​for the refraction of light . Very high values ​​for light refraction (n α  = 2.210; n γ  = 2.390) and a very high value for birefringence (δ = 0.180) were identified on the crystals of Krettnichite . Under the microscope , the mineral is reddish-brown in the incident (reflected) light and, in addition to a clear bireflectance, exhibits a weak pleochroism from very light gray to light brownish gray. With crossed polars, the mineral shows a strong anisotropy with moderate rotational colors in not particularly noticeable shades from dark metallic blue to light blue-gray, silver-colored to light purple-brown-gray.

Krettnichite has a very perfect cleavage according to {001}. Information on tenacity and breakage is missing. With a Mohs hardness of 4.5, the mineral is one of the medium-hard minerals, so it stands between the reference minerals fluorite (hardness 4) and apatite (hardness 5) and, like these, can be easily scratched with a pocket knife more (fluorite) or less (apatite) . The Vickers hardness VHN 100 was determined to be 266-287 kg / mm 2 perpendicular to (001) and 306-383 g / mm 2 parallel to it. The calculated density for krettnichite is 4.51-4.81 g / cm³. The mineral does not fluoresce in long or short-wave UV light .

Krettnichit is potentially unstable in alkaline solutions and is sensitive to alkalis.

Education and Locations

Krettnichit does not form on its type locality, unlike almost all representatives of the Tsumcoritgruppe in the oxidation zone of polymetallic non-ferrous metal - deposits , but in a hydrothermal , mainly of manganite and quartz existing vein . Krettnichite does not represent an alteration product and was not created during a late remobilization phase, but represents a primary mineral that was created during the last stages of the hydrothermal dike formation.

The type locality of the Krettnichit are mining heaps near Krettnich southeast of the town of Wadern in the Merzig-Wadern district in northern Saarland . They belong to a manganese ore deposit that was mined from the middle of the 18th to the beginning of the 20th century. a. via the "Johannschacht" and the "Jakobsstollen". Paragenesis minerals of the krettnichite occurring here in cavities in the duct material are manganite, quartz, barite , ankerite , calcium-containing mottramite , barium-containing brackish bushite and Cu - Co -containing pyrobelonite .

The Krettnich deposit was formed during the interaction of ascending , reducing, metal-rich (Mn, Fe, Ba, Cu, Pb) solutions with oxygen-rich diagenetic waters from the porous Permian conglomerates ("Upper Red lying fishing lomerates"). As a result of the prevailing Eh - pH conditions, manganese oxides and hydroxides separated out, while iron remained in the solution. Mottramite and krettnichite crystallized along with the main ore minerals at the height of the hydrothermal event. While Mottramit was found in the entire area of ​​the Ganges, Krettnichit was only found in its central area. The vanadium probably comes from the Permian side rock (Red Bed Sediments).

As a very rare mineral formation, Krettnichite could only be described from three sites so far (as of 2018). Apart from the type locality in Krettnich these are the "pit Fianel" in the municipality of Ferrera GR belonging Ausserferrera in Val Ferrera , Hinterrheintal , Grisons in Switzerland and the "Fuchsalm-fox lake" area west-northwest of Tweng in Taurachtal , Lungau , Salzburg , Austria .

use

Because of its rarity, krettnichite is a mineral species that is only of interest to mineral collectors.

See also

literature

  • Joël Brugger, Thomas Armbruster, Alan Criddle, Peter Berlepsch, Stefan Graeser, Shane Reeves: Description, crystal structure, and paragenesis of krettnichite, PbMn 3+ 2 (VO 4 ) 2 (OH) 2 , the Mn 3+ analogue of mounanaite . In: European Journal of Mineralogy . tape 13 , 2001, p. 145–158 , doi : 10.1127 / 0935-1221 / 01 / 0013-0145 (English, pdfs.semanticscholar.org [accessed May 27, 2020]).
  • Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 39 , no. 5 , 2001, p. 1484 , doi : 10.2113 / gscanmin.39.5.1473 (English, rruff.info [PDF; 411 kB ; accessed on June 8, 2018]).

Web links

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

Individual evidence

  1. ↑ 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 ac ad ae af ag ah ai aj Joël Brugger, Thomas Armbruster, Alan Criddle, Peter Berlepsch, Stefan Graeser, Shane Reeves: Description, crystal structure, and paragenesis of krettnichite, PbMn 3+ 2 (VO 4 ) 2 (OH) 2 , the Mn 3+ analogue of mounanaite . In: European Journal of Mineralogy . tape 13 , 2001, p. 145–158 , doi : 10.1127 / 0935-1221 / 01 / 0013-0145 (English, pdfs.semanticscholar.org [accessed May 27, 2020]).
  2. ↑ a b Rudolf Duthaler, Stefan Weiß: Clean, prepare and store minerals. The workbook for the collector . 1st edition. Christian Weise Verlag, Munich 2008, ISBN 978-3-921656-70-9 , p. 141 .
  3. ^ Gerhard Müller: Minerals of the Saarland . In: Gerhard Müller (Hrsg.): Der Aufschluss . Saarland. Conference booklet of the VFMG summer conference 1982. Special volume 32. Heidelberg 1982, p. 5-32 .
  4. ↑ a b c Joël Brugger, Hartmut Hensel, Thomas Raber, Klaus Schäfer: Site of rare vanadium minerals: The manganese deposit of Krettnich in Saarland . In: Lapis . tape 26 , no. 11 , 2001, p. 25-33 .
  5. ↑ Catalog of Type Mineral Specimens - K. (PDF 96 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  6. ↑ a b Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , 1998, pp. 179–206 , doi : 10.1127 / ejm / 10/2/0179 (English).
  7. ↑ 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 .
  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 May 27, 2020 .
  9. ^ Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 39 , no. 5 , 2001, p. 1484 , doi : 10.2113 / gscanmin.39.5.1473 (English, rruff.info [PDF; 411 kB ; accessed on June 8, 2018]).
  10. ^ Fabien Cesbron, Jean Fritsche: La mounanaïte, nouveau vanadate de fer et de plomb hydraté . In: Bulletin de la Societe française de Minéralogie et de Cristallographie . tape 92 , 1969, p. 196–202 (French, rruff.info [PDF; 484 kB ; accessed on May 27, 2020]).
  11. ↑ Krettnichite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 27, 2020 .
  12. ↑ a b Gerhard Müller: Thoughts on the mineralization in Saarland . In: The opening . tape 39 , 1988, pp. 257-268 .
  13. ↑ Localities for Krettnichite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 27, 2020 .
  14. ↑ a b List of locations for krettnichite from the Mineralienatlas and Mindat , accessed on May 27, 2020.
  15. ↑ Philippe Roth: Another interesting new find from Fianel (GR): Krettnichit . In: Swiss emitters . tape 2018 , no. 1 , 2018, p. 30–31 ( svsmf.ch [accessed June 8, 2018]).
  16. ↑ Uwe Kolitsch, Tobias Schachinger, Franz Bernhard: Ardennite- (As), ardennite- (V), gasparite- (Ce) and chernovite- (Y): first results of a mineralogical study of the metaradiolarite-hosted manganese ore mineralizations in the Fuchssee area, Radstadt Tauern, Salzburg, Austria . In: Communications from the Austrian Mineralogical Society . tape 161 , 2015, p. 67 (English, uibk.ac.at [PDF; 20.0 MB ; accessed on May 27, 2020]).