Kamotoite- (Y)

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Kamotoite- (Y)
Kamotoite- (Y) -Astrocyanite- (Ce) -Uranophane-180995.jpg
Fan-shaped, slat-like lemon-yellow kamotoite (Y) next to microcrystalline yellow uranophane and blue astrocyanite (Ce) from the Kamoto East Mine in Kamoto, near Kolwezi , Katanga Province , Democratic Republic of the Congo
General and classification
other names

IMA 1985-051

chemical formula Y 2 (UO 2 ) 4 (CO 3 ) 3 (OH) 8 · 10–12 (H 2 O)
Mineral class
(and possibly department)
Carbonates and nitrates
System no. to Strunz
and to Dana
5.EA.30 ( 8th edition : V / F.06)
16b.03.03.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) P 2 1 / a (No. 14)
Lattice parameters a  = 21.22  Å ; b  = 12.93 Å; c  = 12.39 Å
β  = 115.3 °
Formula units Z  = 4
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) 3.93
Cleavage good after {001}, clearly after {010}
colour yellow, lemon yellow
Line color Please complete!
transparency Please complete!
shine Glass gloss
radioactivity very radioactive
Crystal optics
Optical character biaxial negative
Pleochroism X: colorless, Y: pale yellow-green, Z: light yellow

Kamotoite- (Y) is a very rarely occurring mineral from the mineral class of " carbonates and nitrates ". It crystallizes in the form of lemon-yellow, lath-like and fan-shaped crystals in the monoclinic crystal system with the chemical composition Y 2 (UO 2 ) 4 (CO 3 ) 3 (OH) 8 · 10-12 (H 2 O). It is therefore a water-containing , yttrium-rich uranyl carbonate . In addition to yttrium, it contains other rare earth elements such as neodymium , gadolinium , samarium and dysprosium in variable percentages, and is only known from its type locality, the Kamoto East Mine in the Democratic Republic of the Congo .

Etymology and history

Kamotoite- (Y) was first described in 1986 by Michel Deliens and Paul Piret and named after its type locality , the Kamoto East Mine in Kamoto, near Kolwezi in the Democratic Republic of the Congo.

The spelling Kamotoït- (Y) (French Kamotoïte- (Y) ), originally chosen by the first person to describe it , has been discredited since 2008 because the colon above the 'i' ( Trema ) is an unnecessary diacritical mark .

The type mineral is located in the Royal Museum for Central Africa in Tervuren , Belgium .

classification

In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the kamotoite (Y) belonged to the mineral class of "carbonates, nitrates and borates" and there to the "V / F" section of " uranyl carbonates [UO 2 ] 2+ to [CO 3 ] 2− ", where together with astrocyanite- (Ce) , bijvoetite- (Y) , and shabait- (Nd) it formed the unnamed group V / F.06 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the kamotoite (Y) to the mineral class of "carbonates and nitrates" in the "uranyl carbonates" section under the "carbonates" other anions, with H 2 O "with the system no. "5.EA.30". It represents the group of minerals with a ratio of UO 2 : CO 3 = 1: 1 together with the other minerals urrancalcarite , wyartite , wyartite II , oswaldpeetersite , roubaultite and sharpit .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns kamotoite- (Y) to the class of "carbonates - hydroxyl or halogen". Here it is in the unnamed group 16b.03.03.01 within the subdivision " 16b.01 Carbonates - hydroxyl or halogen with (A) m (B) n (XO 3 ) p Z q , with (m + n): p = 1: 1 "to find.

Crystal structure

Kamotoite- (Y) crystallizes in the monoclinic crystal system in the space group P 2 1 / a (space group no. 14) with the lattice parameters a  = 21.22  Å (1 Å = 100  pm ) b  = 12.93 Å and c  = 12 , 39 Å and β = 115.3 ° as well as 4 formula units per unit cell .

properties

The mineral is very radioactive due to its uranium content of up to 53.2 % by weight . Taking into account the natural decay series, a specific activity of about 95.3 k Bq / g is given for kamotoite- (Y) (for comparison: natural potassium 0.0312 kBq / g).

Due to the accompanying rare earth elements, the sum formulas of different mineral samples of Kamotoite- (Y) can differ from one another. For example, the first writers used electron beam microanalysis to determine the content of rare earth elements in relation to the oxides as follows: Y 2 O 3 6.19%, Nd 2 O 3 2.36%, Sm 2 O 3 1.91%, Gd 2 O 3 2, 10% and Dy 2 O 3 1.64%. Raman studies by Čeijka et al. in 2006 confirmed that Kamotoït- (Y) is a hydroxide and not, as initially assumed, an oxide .

Education and Locations

Kamotoite- (Y) from the Kamoto East Mine, DR Congo (image width 5 mm)

Kamotoite- (Y) forms as a secondary uranium mineral in the oxidation zone of primary uranium ores.

The mineral is known in Africa so far only from the type locality Kamoto Ost in Kamoto in the Democratic Republic of the Congo . There it is associated with astrocyanite (Ce) , Francoisite (Nd) , masuyite , schuilingite (Nd) , shabaite (Nd) and uranophane as well as malachite , uraninite , curite , schoepite , becquerelite , rutherfordine , kasolite and soddyite .

Worldwide, the mineral has so far been proven at only six other sites: In the Sophia Mine near Wittichen in the Black Forest, Germany, in Giétroz in the canton of Valais in Switzerland, in Madawaska, Canada, in Jáchymov in the Czech Republic and near Krøderen in Norway.

Precautions

Due to the strong radioactivity of the mineral, mineral samples from kamotoite (Y) should only be kept in dust- and radiation-tight containers, but especially never in living rooms, bedrooms or work rooms. Likewise, because of the high toxicity and radioactivity of uranyl compounds, absorption into the body ( incorporation , ingestion ) should be prevented in any case and, for safety, direct body contact should be avoided and face masks and gloves should be worn when handling the mineral.

See also

literature

  • M. Deliens, P. Piret: La kamotoïte- (Y), un nouveau carbonate d'uranyle et de terres rares de Kamoto, Shaba, Zaïre. In: Bulletin de Minéralogie. , Vol. 109 (1986), pp. 643-647
  • M. Deliens, P. Piret, E. van der Meersche: Les Mineraux Secondaire d'Uranium du Zaïre . Deuxieme Complement. 1990, Institut Royal des Sciences Naturelles de Belgique, p. 11.
  • Kamotoite- (Y) , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( online (PDF 66.5 kB ))

Web links

Commons : Kamotoite- (Y)  - collection of images, videos and audio files

Individual evidence

  1. a b c RL Frost, ML Weier, J. Čeijka, GA Ayoko: Raman spectroscopy of uranyl rare earth carbonate kamotoite- (Y) In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2006, 65, pp. 529-534. ( Abstract )
  2. a b c d e f g Kamotoite- (Y) at Webmineral.com
  3. ^ Mindat - Kamotoite- (Y) at Mindat.org
  4. a b FC Hawthorne, EAJ Burke, TS Ercit, ES Grew, JD Grice, JL Jambor, J. Puziewicz, AC Roberts, DA Vanko: New Mineral Names In: American Mineralogist. 1988, 73, pp. 189-199. ( PDF 1.5 MB )
  5. ^ Ernst AJ Burke: Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks , In: Mineralogical Record , Volume 39, No. 2 (March – April 2008); PDF 2.7 MB