Ludlockite

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Ludlockite
Ludlockite-rw10b.jpg
Ludlockite fibers from the type locality Tsumeb, Namibia ( overall size 3.9 × 2.3 × 1.5 cm)
General and classification
other names

IMA 1969-046

chemical formula PbFe 3+ 4 As 3+ 10 O 22
Mineral class
(and possibly department)
Oxides and hydroxides
System no. to Strunz
and to Dana
4.JA.45 ( 8th edition : IV / J.07)
05/38/04/01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Room group (no.) A 1 (No. 2)
Lattice parameters a  = 10.43  Å ; b  = 12.07 Å; c  = 18.35 Å,
α  = 101.8 °; β  = 100.2 °; γ  = 90.6 °
Formula units Z  = 4
Twinning lamellar according to {0 1 1}
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) measured: 4.33 to 4.40; calculated: 4.58
Cleavage completely mica-like cleavable according to {0 1 1} and {021}
Break ; Tenacity not defined as it is very flexible and can be cut with a knife
colour red, red-brown to orange-brown, yellow
Line color light brown
transparency translucent
shine Greasy sheen, silk sheen
Crystal optics
Refractive indices n α  = 1.960
n β  = 2.055
n γ  = 2.110
Birefringence δ = 0.150
Optical character biaxial positive
Pleochroism visible: X = yellow; Y = dark yellow; Z = orange-yellow

Ludlockite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the triclinic crystal system with the composition PbFe 3+ 4 As 3+ 10 O 22 , so it is chemically a lead - iron - arsenite .

Ludlockite is translucent and develops fibrous to tabular crystals with a fat-like sheen on the surfaces, which are usually arranged in hair-like tufts or felt-like mats and then have a rather silky sheen. Its color varies between red, red-brown to orange-brown and yellow, while its line color is light brown.

With a Mohs hardness of 1.5 to 2, ludlockite is one of the soft minerals that can be scratched with the fingernail , similar to the reference mineral plaster .

Etymology and history

Was first discovered in Ludlockit germanite - ore of the second oxidation zone of " Tsumeb Mine" in the Oshikoto region of Namibia and described in 1970 by RJ Davis, PG Embrey and MH Hey. They named the mineral after two mineral collectors and traders, Frederick Ludlow Smith III and Charles Locke Key, who generously provided Davis and his team with mineral samples for analysis of the material.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the ludlockite belonged to the division of "arsenites (with As 3+ )", where it was the only member of the group of "arsenites with [As x O y ] 4− -Groups "with the system no. IV / J.07 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), classifies ludlockite in the newly defined division of "arsenites, antimonites, bismuthites, sulfites, selenites and tellurites". This is further subdivided according to the possible presence of crystal water and / or additional anions , so that the mineral is classified in the sub-section “Arsenites, Antimonides, Bismutites; without additional anions, without H 2 O “, where it is the only member of the unnamed group 4.JA.45 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns ludlockite to the class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates etc.". Here he is the only member of the unnamed group May 38, 2004 within the sub-section “ Anhydrous phosphates etc., with various formulas ”.

Education and Locations

Ludlockite (orange) on Leiteit (pearl white) from the Tsumeb Mine, Namibia (size: 2.8 × 1.8 × 1.2 cm)
Orange-brown ludlockite suns from the Veta Negra mine, Tierra Amarilla, Province of Copiapó , Región de Atacama , Chile (field of view approx. 3 × 4 mm)

Ludlockite forms in hydrothermal sulphide ore deposits of complex, polymetallic composition. As Begleitminerale occur among other bornite , chalcocite , germanite , Leiteit , quartz , pyrite , Renierit , Schneiderhöhnit , zinc-containing siderite , Stolzit and Tennantit on.

As a rare mineral formation, Ludlockite could only be detected at a few sites, whereby so far (as of 2013) around 20 sites are known. Its type locality "Tsumeb Mine" is the only known site in Namibia to date, but it provided the world's richest mineral samples and the most beautiful collectibles.

In Germany, the mineral is known so far only from the district of Mansfeld-Südharz near the Kupferkammer Hettstedt , the Krughütte near Lutherstadt Eisleben and the Eckardthütte and Lutherhütte near Leimbach (Mansfeld) .

The only place of discovery in Austria so far is the ancient gold pits near Kliening in Lavanttal, Lower Carinthia.

Other sites include the “Veta Negra Mine” in the Pampa Larga District (Tierra Amarilla) in the Chilean province of Copiapó , the slag heaps of the “Les Rats Mine” near Le Crozet in the French region of Auvergne-Rhône-Alpes , and the slag heaps in the Area of Lavrio in the Greek municipality of Attica, the slag heaps in the area of Campiglia Marittima and Piombino in the Italian Tuscany, the "Kiura Mine" near Saeki in the Japanese prefecture of Ōita (Kyūshū) and the "Stavoren-Mutue" tin field in the South African province of Mpumalanga .

Crystal structure

Ludlockite crystallizes triclinically in space group A 1 (space group no. 2) with the lattice parameters a  = 10.43  Å ; b  = 12.07 Å; c  = 18.35 Å; α = 101.8 °; β = 100.2 ° and γ = 90.6 ° as well as 4 formula units per unit cell .

See also

literature

  • RJ Davis, PG Embrey, MH Hey: Ludlockite: A New Arsenate Mineral. In: Mineralogical Society of Japan Special Paper. Volume 1, 1970, pp. 264-264. ( PDF 125 kB )
  • MA Cooper, FC Hawthorne: The crystal structure of ludlockite, PbFe 3+ 4 As 3+ 10 O 22 , the mineral with pentameric arsenite groups and orange hair. In: The Canadian Mineralogist. Volume 34, 1996, pp. 79-89. ( PDF 1 MB )
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 560 (first edition: 1891).

Web links

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

Individual evidence

  1. a b c d e 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.  265 .
  2. Webmineral - Ludlockite
  3. a b Ludlockite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 71.3 kB )
  4. a b Mindat - Ludlockite
  5. Mineral Atlas: Ludlockite
  6. List of localities for ludlockite in the Mineralienatlas and Mindat