Masuyit

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Masuyit
Masuyit - Shinkolobwe.jpg
About 0.5 mm large Masuyite crystal (orange) next to needle-like curite (red) from the Kasolo Mine in Shinkolobwe , Katanga Province , Democratic Republic of the Congo
General and classification
chemical formula Pb [(UO 2 ) 3 | O 3 | (OH) 2 ] • 3H 2 O
Mineral class
(and possibly department)
Oxides and hydroxides
System no. to Strunz
and to Dana
4.GB.35 ( 8th edition : IV / H.03)
02/05/02/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic; m
Room group (no.) Pn (No. 7)
Lattice parameters a  = 13.98  Å ; b  = 12.11 Å; c  = 14.2 Å
β  = 90.402 °
Formula units Z  = 2
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) 5.08
Cleavage completely after {001}, uneven after {010}
colour orange-brown, carmine, red, red-orange
Line color yellow
transparency translucent
shine Glass gloss
radioactivity very strong
Crystal optics
Refractive indices n α  = 1.785
n β  = 1.895
n γ  = 1.915
Birefringence δ = 0.130
Optical character biaxial negative
Axis angle 2V = measured: 50 °; calculated: 44 °
Pleochroism X = light yellow, Y = Z = deep golden yellow

Masuyite is a rarely occurring uranium mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the monoclinic crystal system with the chemical composition Pb [(UO 2 ) 3 | O 3 | (OH) 2 ] · 3H 2 O and develops mostly translucent, prismatic and pseudo-hexagonal crystals of orange-red to carmine-red color.

Etymology and history

Masuyit was first described in 1947 by the Belgian mineralogist Johannes Franciscus Vaes , who named it in honor of the Belgian geologist Gustave Masuy (1905–1945), who dealt with Congolese minerals and was shot by Germans at the end of the Second World War. Vaes has the mineral initially described as a lead uranyl oxide hydrates, further analysis of Deliens however, and Ewing Finch and show variations in the lead - uranium ratio. Investigations on 16 different Masuyit crystals by Deliens and Piret from 1996 show that the Pb-U ratios fluctuate between 1: 3 and 4: 9, so that Masuyit I , Masuyit II and Masuyit III are sometimes used in the literature . In 1999, Burns and Hanchar were able to use single crystal structure analysis to clarify the crystal structure of a masuyite sample from the Shinkolobwe mine in the Democratic Republic of the Congo .

The original type mineral from Masuyit has been lost, but a neo-type mineral is at the Royal Museum for Central Africa in Tervuren , Belgium . Another sample is at Harvard University in Cambridge, Massachusetts, USA, which, although determined by Vaes, has been shown to contain no lead.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the masuyite belonged to the mineral class of "oxides and hydroxides" and there to the department of "uranyl hydroxides and hydrates", where together with Becquerelit , Billietit , Compreignacit and Protasit forms an independent group.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns masuyite to the class of "oxides and hydroxides" and there into the department of "uranyl hydroxides". However, this section is further subdivided according to the presence of further cations and the crystal structure, so that the mineral is classified according to its composition and structure in the sub-section “With additional cations (K, Ca, Ba, Pb etc.), with predominantly UO 2 (O , OH) 5 pentagonal polyhedra “under the system no. 4.GB.35 can be found.

The systematics of minerals according to Dana also assigns the masuyite to the class of "oxides and hydroxides", but there in the department of "uranium and thorium-containing oxides". Here it is with the system no. 05.02.02.01 to be found within the sub-section of " 05.02 Oxides containing uranium and thorium with a cation charge of 6+ (AO 3 ), and containing water ".

Crystal structure

Crystal structure of Masuyit. The connection of the uranyl oxygen atoms by lead __ U __ O __ Pb is shown

Masuyit crystallizes in the monoclinic crystal system in the space group Pn (space group no.7 ) with the lattice parameters a  = 13.98  Å , b  = 12.11 Å, c  = 14.2 Å and β  = 90.402 ° as well as two formula units per unit cell .

In the crystal structure , the uranium atom has a pentagonal-bipyramidal geometry. Layers of edge-linked uranyl units are created, with the uranyl oxygen atoms being coordinated by the lead atoms.

properties

The mineral is very radioactive due to its uranium content of up to 61.9 % by weight . Taking into account the proportions of the radioactive elements in the idealized empirical formula as well as the subsequent decays of the natural decay series, a specific activity of about 110.8 k Bq / g is specified for the mineral (for comparison: natural potassium 0.0312 kBq / g). However, the quoted value can vary significantly depending on the mineral content and composition of the levels; selective enrichment or depletion of the radioactive decay products are also possible and change the activity.

Education and Locations

Masuyite is found as a rare transformation product in the oxidation zone of primary uranium ore deposits. Depending on where it was found, the mineral is associated with uranophane , fourmarierite , rutherfordin , becquerelite , metastudtite , kasolite , wyartite and uraninite .

In addition to the type locality in Shinkolobwe, Masuyit was also found in the Musonoi mine and in the Kamoto East mine. In Switzerland , it was found in Les Marécottes and La Creusaz in the canton of Valais . Other sites in France are the Occitania region in the Hérault department in Rabejac near Lodève and the Auvergne region . It is also known from a few sources in Australia , the Czech Republic , Finland , India , Italy , Poland , Russia and Zambia .

Precautions

Due to the strong radioactivity of the mineral, mineral samples from Masuyit should only be kept in dust- and radiation-proof containers, but above all 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

  • Masuyite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 73.0 kB )

Web links

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

Individual evidence

  1. a b c d Masuyit at Webmineral.com .
  2. a b c d e PC Burns, JM Hanchar: "The structure of masuyite, Pb [(UO 2 ) 3 O 3 (OH) 2 ] (H2O) 3 , and its relationship to protasite" In: "The Canadian Mineralogist" 1999, 37, 1483-1491 ( PDF (English) 956 kB ).
  3. a b c Masuyite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 73.0 kB ).
  4. a b Mindat - Masuyit at Mindat.org .
  5. ^ JF Vaes: Six nouveaux minéraux d'urane provenant de Shinkolobwe (Katanga) , In: Annales de la Société Géologique de Belgique. 1947, pp. B212 to B226 ( PDF (French) 441 kB ).
  6. M. Fleischer: "New mineral names", In: "American Mineralogist" 1948, 33, 384–386 ( PDF (English) 176 kB ).