Mawbyit

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Mawbyit
Mawbyite-Segnitite-170214.jpg
Red-brown mawbyite on yellow segnite from the "Mina do Alto das Quelhas do Gestoso", Gestoso near Manhouce not far from São Pedro do Sul , Viseu district , Portugal (field of view: 0.5 mmm)
General and classification
other names

IMA 1988-049

chemical formula
  • Pb (Fe 2 − x , Zn x ) (AsO 4 ) 2 (OH) 2 − x (H 2 O) x
  • Pb (Fe 1.5 , Zn 0.5 ) (AsO 4 ) 2 (OH) 1.5 (H 2 O) 0.5
  • PbFe 2 (AsO 4 ) 2 (OH) 2
  • Pb (Fe, Zn) 2 [(OH, H 2 O) | AsO 4 ] 2
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.CG.15
02/40/09/04
Similar minerals Arsenic brace bushit
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  = 9.066  Å ; b  = 6.286 Å; c  = 7.564 Å
β  = 114.857 °
Formula units Z  = 2
Frequent crystal faces { 1 01}, {1 1 0}, {001}
Twinning V-shaped twins according to (100)
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) 5.365 (calculated)
Cleavage well parallel {001}
Break ; Tenacity clamshell; not specified
colour pale brown, orange brown, reddish brown (depending on the Fe content)
Line color orange yellow
transparency translucent to translucent
shine Diamond luster
Crystal optics
Refractive indices n α  = 1.940
n β  = 2.000
n γ  = 2.040
Birefringence δ = 0.100
Optical character biaxial negative
Axis angle 2V = 80 ° (measured); 2V = 76 ° (calculated)
Pleochroism weak from brown to reddish brown
Other properties
Chemical behavior sparingly soluble in HCl and H 2 SO 4

Mawbyite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Pb (Fe 1.5 , Zn 0.5 ) (AsO 4 ) 2 (OH) 1.5 (H 2 O) 0.5 and is therefore chemically a water-containing lead - iron - zinc - arsenate with a variable amount of additional hydroxide . The zinc-free end link PbFe 2 (AsO 4 ) 2 (OH) 2 is free of water of crystallization and contains two hydroxide ions.

Mawbyit developed at its type locality drusige, pale orange-brown to reddish brown crust-like aggregates fissures in "Garnet Sandstone", an almost exclusively of Spessartin and quartz existing metamorphic rock, and clothe solution cavities of the massive quartz. In many cases the crusts consist of "dog-tooth-like" crystals with a maximum size of 0.15 mm. The type locality of the mineral is the "Kintore Opencut" opencast mine near Broken Hill in the district of the same name, Yancowinna Co., New South Wales , Australia .

Etymology and history

In the mid-1980s, an arsenic-rich reaction halo was encountered within the main shear zone, which contained a mineral that quickly emerged as a new member of the tsumcorite group, in a thin zone a few cubic meters in size at the southern end of the Kintore open pit mine in Broken Hill, Australia proved. After extensive processing by mineralogists in museums in Adelaide and Melbourne, the new phase was presented to the International Mineralogical Association (IMA), which recognized it as a new mineral in 1988. In 1989 the mineral was described by an international team of scientists led by the Australian mineralogist Allan Pring as well as Elizabeth Maud McBriar and William D. Birch in the US science magazine "The American Mineralogist" as Mawbyite. The authors named the mineral after the Broken Hill born mining entrepreneur Sir Maurice Alan Edgar Mawby CBE (1904–1977) in recognition of his outstanding contributions to the mining industry in Australia and his knowledge of Broken Hill minerals and his efforts to preserve them.

As early as the 1970s and 1980s, steps with so-called “red tsumcorite” were found in the “Tsumeb Mine”. Although it was assumed that it was the mineral Mawbyite, this could not be substantiated analytically at the time. The first record of Mawbyite for Tsumeb comes from 2000 (Professor Terry Seward in a private communication to Rob Lavinsky on December 23, 2004).

The type material for Mawbyite is kept under catalog numbers M39178 (Cotyp) and G16066 (Cotyp) in the collections of the Melbourne Museum (formerly Museum Victoria) in Melbourne and the South Australian Museum in Adelaide , South Australia , both in Australia.

classification

The current classification of the International Mineralogical Association (IMA) counts the mawbyite 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 Mawbyit still Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite .

Since the Mawbyite was only recognized as an independent mineral in 1988, it is not listed in the 8th edition of the mineral classification according to Strunz, which has been outdated since 1977 . Only in the Lapis mineral directory , which was revised and updated in 2018 by Stefan Weiß, which is still based on this classic system from Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system and mineral number. VII / C.31-60 . 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 mawbyite together with cabalzarite, cobalt solder armeyerite, cobalt sumcorite, ferrilotharmeyerite, gartrellite, helmutwinklerite, krettnichite, Lotharmeyerit, Lukrahnit, Manganlotharmeyerit, Mounanait, Nickellotharmeyerit, Nickelschneebergit, Nickeltsumcorit, Phosphogartrellite, Rappoldit, Schneebergite, Thometzekit, Tsumcorit, Yancowinnait and zinc gartrellite form the "Tsumcorite /" Gartrellite group.

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns mawbyite 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 (RO 4 ) to the water of crystallization content , so that the mineral can be classified in the sub-section “With large and medium-sized cations; RO 4  : H 2 O = 1: 1 ”is to be found, where together with cabalzarite, cobalt solder armyerite, cobalt sumcorite, ferrilotharmeyerite, krettnichite, Lotharmeyerite, manganese solder armyerite, mounanaite, nickelotharmeyerite, nickel snow mountainite, snow mountainite“, Thometzekit and tsumcorite with the Tsumcorite group ” System no. 8.CG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns mawbyite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here it is together with cobalt sumcorite, helmutwinklerite, nickel schneebergite, rappoldite, snow mountainite, Thometzekit and tsumcorite in the " Helmutwinklerite subgroup " with the system no. 02/40/09 within the subsection “Phosphates containing water, etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O)”.

Chemism

A microprobe analysis on a copper-free Mawbyite crystal showed values ​​of 37.91% PbO; 23.66% Fe 2 O 3 ; 0.82% ZnO; 0.02% Al 2 O 3 ; 34.90% As 2 O 5 ; 0.23% P 2 O 5 and 2.46% H 2 O (calculated). On the basis of ten oxygen atoms , the empirical formula Pb 1.11 (Fe 3+ 1.94 Zn 0.07 ) , 99 = 2.01 [(As 0.99 P 0.01 ) Σ = 1.00 is calculated from them O 4 ] 2 (OH) 1.79 . The empirical formula from the mean values ​​of all analyzes published in the first description is Pb 1.03 (Fe 3+ 1.49 Zn 0.53 Cu 0.02 Al 0.02 ) Σ = 2.06 (As 1.95 P 0, 01 ) Σ = 1.96 H 2 O 10 , which can be simplified to Pb (Fe 1.5 , Zn 0.5 ) (AsO 4 ) 2 (OH) 1.5 (H 2 O) 0.5 . The ideal formula for the zinc-free end link is PbFe 2 (AsO 4 ) 2 (OH) 2 , which contains 35.38% PbO; 25.33% Fe 2 O 3 ; Requires 36.44% As 2 O 5 and 2.85% H 2 O.

The chemical variability of mawbyite takes place primarily on the Me (2) position, including Fe 3+ , Zn 2+ , Cu 2+ and Al 3+ . As a result, mixed crystal formation is widespread in the crystals at the Me (2) position with the inclusion of the bivalent and trivalent elements mentioned. The mixed crystal formation at the mentioned position is accompanied by a coupled substitution according to M 3+ + OH - ↔ M 2+ + H 2 O. In mawbyite, it is mainly Fe 3+ + OH - ↔ Zn 2+ + H 2 O, which shows that the Zn-free end member is free of water of crystallization and contains only hydroxide ions.

Mawbyite is the Fe 3+ -dominant analogue of the Zn-dominated tsumcorite.

Crystal structure

Crystal structure of mawbyite. Projection in direction [010].
Crystal structure of mawbyite. Projection in direction [001].

Mawbyite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 9.066  Å ; b  = 6.286 Å; c  = 7.564 Å and β = 114.857 as well as two formula units per unit cell . Template: room group / 12

The crystal structure of the mawbyite is identical to the structure of the other representatives of the tsumcorite group. It consists of infinite chains of Fe (O, OH) 6 - octahedra with common edges parallel to the b-axis [010], which are linked to one another via (AsO 4 ) - tetrahedra and in this way form a layer parallel to the Form axes spanned area with the composition [Fe (O, OH) 6 AsO 4 )]. Within the chains, the FeO 6 octahedra have common edges along the mirror plane at y = 0 and 0.5. The adjacent crystal structure drawing, a projection in the direction of the b-axis [010], shows the connection between the parallel octahedron chains. Two corners of the AsO 4 tetrahedra share O atoms with the FeO 6 octahedra and another corner shares an oxygen atom with an FeO 6 octahedron in the next chain. The remaining O (4) atom at the fourth corner of the AsO 4 tetrahedron is only connected to Pb and As. In mawbyite, Pb 2+ is coordinated with eight oxygen atoms, which are arranged along the corners of a distorted square antiprism with an average Pb-O bond length of 2.70 Å. The Pb coordination is more symmetrical in mawbyite than in most other lead oxy salts.

Mawbyite is isotypic (isostructural) to the monoclinic representatives of the tsumcorite group such as tsumcorite and natrochalcite. He is also the monoclinic dimorph to the orthorhombic carminite .

properties

morphology

Mawbyit can be found in different crystal habit variants due to its type locality . It often develops "dog-tooth-like" crystals with a maximum size of 0.15 mm. The surface forms { 1 01}, {1 1 0}, the basic pinacoid {001} are only subordinate to the development of the costume . Mawbyite also forms coatings and scattered aggregates of elongated, prismatic crystals up to 0.2 mm in length, hemispherical, cylindrical and sheaf-shaped aggregates with a flat, spongy appearance and thin, compact crusts. Tabular crystals form V-shaped twins with (100) as the twin plane. During precipitation near Bärenstein in the Saxon Ore Mountains, Mawbyit forms tiny panels that come together like a lawn or have grown together to form rosette-shaped aggregates up to 0.5 mm in diameter.

physical and chemical properties

The crystals of mawbyite are pale brown, orange-brown or reddish-brown, depending on their Fe content. The pure Fe end link is light reddish brown, while the crystals with the highest Zn content (Fe: Zn ≈ 1: 1) are orange-brown in color. Their line color , however, is always orange-yellow. The surfaces of the translucent to transparent crystals have a diamond-like sheen , which agrees well with the values ​​for light refraction . High to very high values ​​for light refraction (n α  = 1.940; n β  = 2.000; n γ  = 2.040) and for birefringence (δ = 0.100) were found on the crystals of mawbyite . Under the microscope , the mineral shows a weak pleochroism from brown to reddish-brown in the transmitted light .

Mawbyite has good cleavage parallel {001}. It breaks in a similar way to quartz , with the fracture surfaces being shell-shaped. With a Mohs hardness of 4, the mineral is one of the medium-hard minerals and, like the reference mineral fluorite, can be easily scratched with a pocket knife. The calculated density for mawbyite is 5.365 g / cm 3 . The mineral is neither in the long term nor in the short wavelength UV light , a fluorescent .

Mawbyite is difficult to dissolve in hydrochloric acid , HCl, and sulfuric acid , H 2 SO 4 .

Education and Locations

Red mawbyite crystals on a dark matrix from the Tsumeb mine (size: 1.9 × 1.5 × 0.9 cm)

Mawbyit is a typical secondary mineral , which as the most representative of Tsumcoritgruppe in the oxidation zone of arsenic-rich polymetallic non-ferrous metal - deposits formed. At its type locality, a metamorphosed stratiform lead-zinc ore body, it was found in an arsenic-rich reaction halo within the main shear zone "Main Shear" on fissures and in cavities of a Spessartine - quartz rock. In the Moldava deposit, Czech Republic, it occurred in the oxidation zone of an Ag – Pb – Cu – Bi mineralization in fluorite – barite – quartz veins; its occurrence at the “Clara pit” is very similar.

The most striking paragenesis mineral of the Mawbyite in Broken Hill is a yellowish-green representative of the Corkite - Beudantite solid solution series. Other accompanying minerals grown together with mawbyite or occurring in its immediate vicinity are adamin - olivite , fragranceite , mimetesite , bayldonite , hidalgoite , pharmacosiderite and a then unknown Cu-Fe-Pb arsenate (gartrellite?). Manganese oxides or goethite form the matrix for mawbyite in Broken Hill. In Moldava, mawbyite is accompanied by mimetesite, philipsbornite and thometzekite . In Tsumeb in crust-forming aggregates of red mawbyite crystals <1 mm on tennantite-rich ore together with etched, tan-colored wulfenite. In the Tsumeb Mine, it was formed from sulphides containing lead and zinc, such as galena and sphalerite , the arsenic originating from the decomposition of the arsenic ore tennantite . Beudantite-segnitite, quartz, bayldonite and stolzite are among the companions in the “Grube Clara” .

As a very rare mineral formation, Mawbyite could only be described from about 20 sites so far (as of 2018). The type locality of the Mawbyite is the large open-cast mine of the Kintore Opencut near Broken Hill, known for its numerous secondary minerals, in the district of the same name, Yancowinna Co., New South Wales , Australia , in which from the late 1980s to 1996 Pb-Zn- (Ag) -Ores have been mined. Other sites for Mawbyit in Australia are the "Pinnacles Mine" in the Broken Hill District, Yancowinna Co., New South Wales, and the "Bali Lo" copper prospect located 11 km west-southwest of the Ashburton Downs homestead, Capricorn Range in Western Australia .

In Germany , Mawbyit is from the Clara mine in the Rankach valley near Oberwolfach , from the Pb-Cu mining district in the Freiamt district , Emmendingen , from the Cu (-Ag-Pb) - "Silberbrünnle mine", Haigerachtal, Gengenbach , and from the Pit "St. Josefi ”in the Schuttertal near Reichenbach not far from Lahr , all known in the Black Forest , Baden-Württemberg . Furthermore Mawbyit is in the pit "Strasbourg luck" in the area Rainfall Bärenstein, precipitation in Bärenstein and in stockpiles of "Pucherschacht" in the mine field "Wolfgang Maassen" and in the pit box "Am Rotenberg," both in Schneeberg in the Erzgebirge , Saxony , salvaged been.

In Greece , the mineral was found in shaft No. 132 (Christiana 132) of the "Christiana" mine near Agios Konstantinos (Kamariza) not far from Plaka ( modern Greek Ορυχείο Χριστιάνα, Αγ. Κωνσταντίνος (Καμάριζα) ), Lavrion mining district , Attica region . In Europe also from the “Mina do Alto das Quelhas do Gestoso”, Gestoso near Manhouce not far from São Pedro do Sul , Viseu district , Portugal , the “Bakara” mine in the Balkan Mountains (Stara Planina), Wraza Oblast , Bulgaria , from Moldava near Dubí (Eichwald), Krušné Hory (Ore Mountains) , Ústecký kraj , Czech Republic , from the corridor “Le Mazet” and the “Mine des Montmins” (“Filon Ste Barbe”), both near Échassières not far from Ébreuil am Allier , Auvergne-Rhône region. Alpes , France and the Old Sandbed Mine, Caldbeck Fells, Cumbria , England , United Kingdom . The occurrence of Mawbyit on the Sperkerriegel near Wiesmath in Buckligen Welt , Lower Austria , Austria is questionable. There are no known occurrences of Mawbyite in Switzerland .

After all, the mineral is known from the Tsumeb Mine , Tsumeb , Oshikoto Region , Namibia , and the "Black Pine Mine" ("Combination Mine") in the Black Pine Ridge within the John Long Mts, Philipsburg District, Granite County , Montana , USA .

use

Due to its rarity, mawbyite is a sought-after mineral for mineral collectors.

See also

literature

  • Allan Pring, Elizabeth Maud McBriar, William D. Birch: Mawbyite, a new arsenate of lead and iron related to tsumcorite and carminite, from Broken Hill, New South Wales . In: The American Mineralogist . tape 74 , no. 12 , 1989, pp. 1377-1381 ( rruff.info [PDF; 603 kB ; accessed on August 29, 2019]).
  • Kharisun, Max R. Taylor, DJM Bevan, Alan David Rae, Allan Pring: The crystal structure of mawbyite, PbFe 2 (AsO 4 ) 2 (OH) 2 . In: Mineralogical Magazine . tape 61 , 1997, pp. 685–691 , doi : 10.1180 / minmag.1997.061.408.07 ( rruff.info [PDF; 449 kB ; accessed on August 29, 2019]).
  • Mawbyite . 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; 68 kB ; accessed on August 29, 2019]).

Web links

Commons : Mawbyite  - 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 ak al am Allan Pring, Elizabeth Maud McBriar, William D. Birch: Mawbyite, a new arsenate of lead and iron related to tsumcorite and carminite, from Broken Hill, New South Wales . In: The American Mineralogist . tape 74 , no. 12 , 1989, pp. 1377–1381 ( rruff.info [PDF; 589 kB ; accessed on May 26, 2018]).
  2. ^ 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.  485 .
  3. ↑ a b c d e f Mawbyite. In: mindat.org. Hudson Institute of Mineralogy, accessed August 29, 2019 .
  4. ↑ a b c d Kharisun, Max R. Taylor, DJM Bevan, Alan David Rae, Allan Pring: The crystal structure of mawbyite, PbFe 2 (AsO 4 ) 2 (OH) 2 . In: Mineralogical Magazine . tape 61 , 1997, pp. 685–691 , doi : 10.1180 / minmag.1997.061.408.07 ( rruff.info [PDF; 439 kB ; accessed on May 26, 2018]).
  5. ↑ a b c d e f g h i j k Mawbyite . 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; 68  kB ; accessed on August 29, 2019]).
  6. ↑ 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. 174 .
  7. ↑ Georg Gebhard: Tsumeb . 1st edition. GG Publishing, Grossenseifen 1999, p. 250 .
  8. ^ A b Ian Bruce, Malcolm Southwood, Liam Schofield: Mawbyite. In: tsumeb.com. Retrieved August 29, 2019 .
  9. ↑ Catalog of Type Mineral Specimens - M. (PDF 124 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  10. ↑ 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 .
  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 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed August 30, 2019 .
  13. ↑ a b Mirko Martin, Fritz Schlegel, Jürgen Siemroth: The mining area precipitation near Oberwiesenthal. Rare copper arsenates from the Saxon Ore Mountains . In: Lapis . tape 19 , no. 4 , 1993, p. 13-22 .
  14. ^ A b Gregor Markl: Achwarzwald. Deposits and minerals from four centuries . 1st edition. 1 Northern Black Forest and Clara Pit. Bode Verlag, Salzhemmendorf 2015, ISBN 978-3-942588-17-1 , p. 402 .
  15. ↑ Localities for Mawbyite. In: mindat.org. Hudson Institute of Mineralogy, accessed August 29, 2019 .
  16. ↑ a b c List of locations for Mawbyite in the Mineralienatlas and Mindat
  17. ^ Type locality Broken Hill, Broken Hill district, Yancowinna Co., New South Wales, Australia. In: mindat.org. Hudson Institute of Mineralogy, accessed August 29, 2019 .
  18. ↑ Joachim Gröbner: Red scorodite and other unusual arsenates: The minerals from mining 132 of the Christiana pit, Lavrion / Greece . In: Lapis . tape 26 , no. 11 , 2001, p. 13-21 .