Caribibit

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Caribibit
Karibibite-203812.jpg
Radial-spherical caribite on quartz from the Oumlil Mine, Bou Azzer (near Tazenakht ), Ouarzazate Province, Souss-Massa-Draâ, Morocco (image width 3.4 mm)
General and classification
other names

IMA 1973-007

chemical formula Fe 3+ 2 As 3+ 4 O 9
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.JA.15
07.10.02.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol Please complete!
Lattice parameters a  = 27.91  Å ; b  = 6.53 Å; c  = 7.20 Å
Formula units Z  = 6
Physical Properties
Mohs hardness "Very soft" (about 1 to 2)
Density (g / cm 3 ) measured: 4.07; calculated: 4.04
Cleavage possibly after {100} or {010}
Break ; Tenacity undefined, crystals flexible
colour brownish yellow to brownish orange
Line color yellow
transparency transparent to translucent
shine Please complete!
magnetism paramagnetic
Crystal optics
Refractive indices n α  = 1.960
n β  = 2.100
n γ  = 2.100
Birefringence δ = 0.140
Optical character biaxial negative
Pleochroism weak: X = Y = straw yellow; Z = light brown yellow
Other properties
Special features occasional yellow fluorescence under short-wave UV light

Karibibite is a rarely occurring mineral from the mineral class of the "oxides and hydroxides (including V [5,6] vanadates, arsenites, sulfites, selenites, tellurites and iodates)". It crystallizes in the orthorhombic crystal system with the idealized composition of Fe 3+ 2 As 3+ 4 O 9 and is thus chemically seen a iron - arsenite . Since the oxygen in naturally formed Karibibiten however, in part, by hydroxide ions replaced may be the formula in various sources, also with Fe 3+ 2 As 3+ 4 (O, OH) 9 indicated.

Karibibit mostly develops only millimeter-sized, fibrous to needle-like crystals , which are mainly arranged in the form of spindle-shaped fiber bundles, radial to spherical mineral aggregates or form crusty coatings. Its color varies between brownish yellow and brownish orange. However, the mineral always leaves a bright yellow line on the marking board .

Etymology and history

The mineral was first discovered in the lithium pegmatites near the municipality of Karibib in the Erongo region in western Namibia and described in 1973 by Oleg von Knorring (1915–1994), Thure Georg Sahama (1910–1983) and Pentti Rehtijärvi , who wrote it named after its type locality .

The type material of the mineral is stored in the Department of Earth Sciences at the University of Leeds in England and the Department of Earth Sciences at the University of Helsinki in Finland.

classification

The caribibite is not yet listed in the outdated 8th edition of the mineral classification according to Strunz . 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. IV / J.08-10 . In the "lapis system" this corresponds to the class of "oxides and hydroxides" and there the section "arsenites (with As 3+ )", where caribibite together with lazarenkoite form the group of "arsenites with [As x O y ] groups + Chains "with the system no. IV / J.08 forms.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns caribibite to the class of “oxides and hydroxides”, but in the class of “arsenites, antimonites, bismuthites” , Sulfites, selenites, tellurites; Iodate ”. This is further subdivided according to the possible presence of additional anions and water of crystallization , so that the mineral is classified according to its composition in the sub-section “Arsenite, Antimonite, Bismutite; without additional anions, without H 2 O ”, where it is the only member of the unnamed group 4.JA.15 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , assigns the caribibite to the class of "oxides and hydroxides", but there in the department and subdivision of the same name of " multiple oxides ", where it is the only member of the unnamed group 07.10 .02 can be found.

Crystal structure

Karibibit crystallizes orthorhombically with the lattice parameters a  = 27.91  Å ; b  = 6.53 Å and c  = 7.20 Å and 6 formula units per unit cell . The space group has not yet been specified.

properties

Karibibit is paramagnetic , so it only builds up its own magnetic field under the influence of an external magnetic field. Some caribibites can also show yellow fluorescence under short-wave UV light .

The mineral is easily soluble in dilute acids and alkali hydroxide solutions .

Education and Locations

Yellowish caribibite as a crack filling in a 2.2 cm × 1.8 cm mass from the Oumlil Mine, Bou Azzer, Morocco
Light yellow, spherical caribibite from the Urucum mine, Galiléia , Minas Gerais , Brazil ( overall size : 3.5 cm × 2.1 cm × 1.2 cm)

Caribibite is secondary to the weathering of lollingite in granitic pegmatites . In addition to lollingite, eosphorite , parasymplesite , quartz , Schneiderhöhnite and scorodite can occur as accompanying minerals .

As a rare mineral formation, caribibite could only be detected at a few sites, with around 15 sites known so far (as of 2014). Its type locality Karibib is the only known site in Namibia to date .

Other previously known localities are the Almerindo mine at Linópolis and the Boca Rica claim and the urucum mine at Galiléia in Docetal (Minas Gerais) in Brazil, the Veta Negra mine in the Pampa Larga (Tierra Amarilla, Copiapo) in the Chilean de Región Atacama , the Kiura mine near Saiki ( Saeki ) in the Japanese prefecture of Ōita (Kyūshū), the Kalba Range in eastern Kazakhstan , several mines in the district of Bou Azer ( Bou Azzer ) near the city of Tazenakht in the Moroccan province of Ouarzazate (Souss-Massa-Draâ) and a granite quarry near Tuften (Tvedalen) in the Norwegian province of Vestfold .

In 2004, in Bou Azer, Morocco, excellent and densely populated specimens with centimeter-sized caribibite crystals were found.

See also

literature

Web links

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

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: September 2019. (PDF 2672 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed September 16, 2019 .
  2. ^ A b c 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.  264 (English).
  3. ↑ a b 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 .
  4. ↑ a b c d e Karibibite . 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; 71  kB ; accessed on September 16, 2019]).
  5. ↑ a b c d Karibibite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 16, 2019 .
  6. ↑ a b Mineralienatlas: Karibibit
  7. ^ Peter H. Nixon: Oleg von Knorring . In: Mineralogical Magazine . tape 58 , 1994, pp. 693–694 (English, rruff.info [PDF; 775 kB ; accessed on September 16, 2019]).
  8. ^ Ilmari Haapala: Memorial of Thure Georg Sahama . In: American Mineralogist . tape 70 , 1985, pp. 433–435 (English, minsocam.org [PDF; 312 kB ; accessed on September 16, 2019]).
  9. ^ Oleg von Knorring, Thure Georg Sahama, Pentti Rehtijärvi: Karibibite , a new FeAs mineral from South West Africa . In: Lithos . tape 6 , 1973, p. 265-272 , doi : 10.1016 / 0024-4937 (73) 90087-X (English).
  10. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 16, 2019 .
  11. ↑ Michael Fleischer , JA Mandarino: New mineral names . In: American Mineralogist . tape  59 , 1974, pp. 381–384 (English, rruff.info [PDF; 478 kB ; accessed on September 16, 2019] Karibibite from p. 2).
  12. ↑ 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.  801 .
  13. ↑ Localities for Karibibit. In: mindat.org. Hudson Institute of Mineralogy, accessed September 16, 2019 .
  14. ↑ Find location list for caribibite at the Mineralienatlas and at Mindat , accessed on September 16, 2019.