Kasolite

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Kasolite
Kasolite-156559.jpg
Kasolite from the Musonoi Mine , Katanga , Democratic Republic of the Congo
General and classification
chemical formula Pb [UO 2 | SiO 4 ] • H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.AK.15 ( 8th edition : VIII / B.34)
53.03.01.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic
Room group (no.) P 2 1 / a (No. 14)
Lattice parameters a  = 6.704  Å ; b  = 6.932 Å; c  = 13.252 Å
β  = 104.22 °
Formula units Z  = 4
Physical Properties
Mohs hardness 4 to 5
Density (g / cm 3 ) 5.96 to 6.50
Cleavage completely after {001}, indistinct after {100} {010}
Break ; Tenacity brittle
colour yellow-orange, reddish-orange, ocher-yellow
Line color light brownish yellow
transparency transparent to translucent
shine Glass gloss, wax gloss to matt
radioactivity very strong
Crystal optics
Refractive indices n α  = 1.890
n β  = 1.910
n γ  = 1.950
Birefringence δ = 0.060
Optical character biaxial positive
Axis angle 2V = 32 to 45 °
Pleochroism weak: X and Y = weak yellow; Z = colorless to pale gray

The mineral kasolite is a rather seldom occurring uranium mineral with the chemical composition Pb [UO 2 | SiO 4 ] • H 2 O. It crystallizes in the monoclinic crystal system and develops mostly needle-prismatic, yellow-orange crystals . Granular to massive mineral aggregates or crusty coatings show an ocher-brown to reddish-brown color.

Etymology and history

Kasolit was first described by Alfred Schoep in 1921 . The structure of Kasolit was first determined in 1963. Kasolit is named after its type locality, the Kasolo Mine in Shinkolobwe , Democratic Republic of the Congo .

The type mineral is in the Natural History Museum (catalog no. 121.287) in Paris .

classification

The outdated 8th edition of the Strunz lists the Kasolit in the "Uranophangruppe" with the system no. VIII / B.34 and the other members Boltwoodit , Cuprosklodowskit , Natroboltwoodit , Oursinit , Sklodowskit , Uranophan and Uranophan-beta .

The 9th, completely revised edition of Strunz lists the kasolite in the section K "Uranyl island and sheet silicates with a uranium: silicon ratio of U: Si = 2: 1" in group 9.AK.15 . This group includes the other uranyl silicates boltwoodite, natroboltwoodite, uranophane and uranophane-beta.

The systematics of minerals according to Dana , which is common in the English-speaking world , assigns the kasolite to the uranophane group of the island silicates department, but there in the department of " island silicates with SiO 4 groups and other anions as well as complex cations with (UO 2 ) " with the system No. 53.03.01.01 a.

Crystal structure

Kasolit crystallizes monoclinically in the space group P 2 1 / a (space group no. 14) with the lattice parameters a  = 6.704  Å ; b  = 6.932 Å; c  = 13.252 Å and β = 104.22 ° as well as 4 formula units per unit cell . The uranyl groups form a layer structure with the SiO 4 tetrahedra, so that the uranyl ion has a pentagonal-bipyramidal coordination of oxygen atoms. These "uranyl silicate" layers are connected to one another by the lead atoms . Each lead atom coordinates four silicate oxygen atoms and one uranyl oxygen atom. Two Pb atoms are linked to one another via two different silicate oxygen atoms. The four silicate oxygen atoms also each have a different coordination. One silicate oxygen atom coordinates two Pb atoms, the second coordinates two U atoms, the third coordinates one Pb and one U atom and the fourth coordinates two U atoms and one Pb atom.

  • Packing structure of kasolit in the direction of the crystallographic b-axis (water molecules removed for clarity) ( __ U __ O __ Pb __ Si )

  • Detail of the packing structure of Kasolit (water molecules removed for clarity) ( __ U __ O __ Pb __ Si )

properties

Different colors of the Kasolit depending on the location; above: Musonoi, below: Shinkolobwe (both mines, Katanga Province, DR Congo)

Due to its uranium content of up to 40.6%, kasolite is considered to be very radioactive . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the subsequent decays of the natural decay series, a specific activity of 72.5 k Bq / g is specified for the mineral (for comparison: natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and the composition of the levels; selective enrichment or depletion of the radioactive decay products is also possible and changes the activity.

Kasolit can be dissolved by acids .

Education and Locations

Paragenesis of orange-yellow, prismatic kasolite next to dark green, tabular torbernite from the Musonoi mine , Kolwezi , Katanga , Democratic Republic of the Congo

Kasolite is a rather rare uranium mineral. It occurs in the weathering zone of primary uranium ores and, in addition to the type locality in the Democratic Republic of the Congo, was also found in Germany in Menzenschwand in the Krunkelbach mine and in Oberwolfach in the Clara mine . However, the best quality finds of Kasolite in Germany come from Schurf 5 in Tirpersdorf , Vogtlandkreis where canary hedgehogs and radialstrahlige bask in drusen or cleavage surfaces of the slate next Torbernit / Zeunerit - mixed crystals found. Other locations include Tsumeb ( Namibia ), Franceville ( Gabon ), Lodève ( France ) and Příbram ( Czech Republic ).

Kasolit is associated with uraninite , curite , torbernite and dewindtite ( Kasolo Mine , Democratic Republic of the Congo) as well as with rutherfordin , Sklodowskite and Curit ( Nabarlek Mine , Australia).

Precautions

Due to the toxicity and the strong radioactivity of the mineral, mineral samples from Kasolit should only be kept in dust and radiation-tight containers, but especially never in living rooms, bedrooms or work rooms. Absorption into the body (incorporation, ingestion ) should also be prevented in any case and, for safety, direct body contact should be avoided and respiratory protection mask and gloves should be worn when handling the mineral .

See also

literature

Web links

Commons : Kasolite  - 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. 565 .
  2. ↑ a b Webmineral - Kasolite (English)
  3. ↑ a b c Kasolite at mindat.org (engl.)
  4. ^ A b Francis V. Stohl, Deane K. Smith: The crystal chemistry of the uranyl silicate minerlas In: American Mineralogist. 1981, 66, pp. 610–625 ( PDF; 1.59 MB )
  5. ↑ Joachim Gröbner, Uwe Kolitsch: Rare minerals from Uranschurf Tirpersdorf in the Saxon Vogtland. In: Lapis 32, 2007 (1), pp. 37-42.